PCPIC. Multi-Counter/Timer Board. Technical Manual. Revision History Section 1. Introduction Section 2. The PCPIC I/O Map...

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1 J230 PCPIC PCPIC Multi-Counter/Timer Board Technical Manual Revision History Section 1. Introduction The PCPIC About the PC Features of the PCPIC Using Signal-Conditioning Boards What to do Next Section 2. The PCPIC I/O Map The I/O Pointer Scheme How the PCPIC Appears in PCbus I/O Space The Registers on the PCPIC How to Write to the Registers Counter Registers Counter Modes Other Registers Section 3. Using the PCPIC Installing the PCPIC Addresses Installing Multiple PCPICs A Quick Installation Test Links Link position Diagram Connections Digital I/O Frequency Outputs Measuring Frequency Counting Measuring Time Page 1

2 J230 PCPIC Interrupts Fault Finding Section 5. Software Section 6. Circuit Description Installation for CE Compliance Appendix A. Specification Appendix B. Connections Appendix D: Circuit Diagrams Page 2

3 J230 PCPIC Revision History Manual V1 Iss 2b V1 Iss 3 V1 Iss 4 Issue A Issue B PCB V1 Iss 2 V1 Iss 2a V3 Iss 1 V3 Iss 1a Comments Manual first released in this format Edits to pages 12,17-21 [ECO591] Minor Modification, New Circuit Diagram [ECO1803] [ECO2179 & ECO2691] [ECO2684 & ECO2696] Arcom Control Systems Ltd 1997 The choice of boards and systems is the responsibility of the buyer, and the use to which they are put cannot be the liability of Arcom Control Systems Ltd. However, Arcom s team is always available to assist you in making your decision. Arcom Control Systems Ltd is a subsidiary of Fairy Group plc. Specifications are subject to change without notice and do not form part of any contract. All trademarks recognised. Arcom Control Systems Ltd operate a company-wide quality management system which has been certified by the British Standards Institution (BSI) as compliant with ISO 9001:1994. Product Information Full information about other Arcom products is available via the Fax on Demand System, (Telephone numbers are listed below), or by contacting our Website at: Additional useful contact information: Customer Support: (tel) +44 (0) , (fax) +44 (0) , ( ) support@arcom.co.uk Sales: (tel) +44 (0) , (fax) +44 (0) , ( ) sales@arcom.co.uk, or for the US, icpsales@arcomcontrols.com United Kingdom Arcom Control Systems Ltd Clifton Road Cambridge CB1 4WH UK tel: +44 (0) fax: +44 (0) FoD: United States Arcom Control Systems Inc South Oak Street Kansas City, MO USA tel: (toll free) fax: FoD: France Arcom Control Systems Centre d affaires SCALDY 23, rue Colbert 7885 SAINT QUENTIN Cedex, FRANCE tel:(numero Vert) fax:(numero Vert) FoD:(Numero Vert) Germany (Kostenlose Infoline:) tel: fax: FoD: Italy FoD: Belgium (Groen Nummer:) tel: fax: Netherlands (Gratis 06 Nummer:) tel: fax: Page 3

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5 J230 PCPIC Section 1. Introduction The PCPIC The PCPIC is an I/O board for PC-compatibles. It uses three 8254 counter chips and some extra logic to measure 8 channels of frequency, counts or time. It also has up to 16 digital input lines, 8 digital output lines, 8 lines of counter output and 8 interrupt inputs. It is designed for connecting to pieces of industrial plant and equipment and is compatible with Arcom's signal-conditioning scheme. This manual describes the PCPIC, its uses, connections and software. About the PC PC-compatibles are often used for I/O intensive applications with boards such as the PCPIC. Unfortunately, some features of the PC can make life difficult for users. We have tried to address these problems with the PCPIC. For example, it is sometimes difficult to find I/O address space in a PC - we have created a unique pointer addressing scheme which only takes up two bytes of PC I/O space but allows hundreds of I/O locations on the board. Another common problem is that of getting large numbers of cables safely into a PC. Arcom designed a signal-conditioning system which has been in use on other buses for some years; this system is also available for the PCPIC. Features of the PCPIC The PCPIC can perform many functions, although not necessarily all at once. Many of the functions are concerned with counting - either counting pulses in a fixed time interval (frequency measurement), counting a fixed clock for a variable time (time measurement) or simply counting and totalising input pulses. The three 8254 chips on the PCPIC contain a total of nine 16-bit counters to perform the counting. Of these nine, eight can be connected to the input pins on the connector in some way, and the remaining one is used as a timebase. The eight counters are in two sets of four; each set is independent, although they do share the same timebase. The clock for the timebase can be jumper-selected as either 1MHz or 25kHz. This can then be divided down by up to in the timebase counter to give a very wide range of possible timebase outputs. Generally, the higher frequencies are used for time measurement and the lower ones for frequency measurement. It is not just the timebase frequency that is programmable; what the timebase output does can also be controlled by software. For example, it can be used to open the counter gates for a precisely determined time period - this is the basis of frequency measurement. Alternatively, an external signal can open the counter gates while a Page 5

6 J230 PCPIC Using Signal-Conditioning Boards known frequency from the timebase is counted, so times can be measured. The counter gates determine whether the counters can count or not. In some cases - for example free-running counters - they can be permanently open. In other cases - for example measuring the time between two signals - the gates must be opened by one signal and closed by another. To cope with this case, the PCPIC has eight latches which can be set and reset by pairs of signals. As can be seen, a fair amount of 'rewiring' is necessary to configure the PCPIC to perform these different functions. This is all achieved by setting up bits in a register on board and changing the mode of operation of the counters. The PCPIC can also be used for digital I/O. One group of eight lines on the connector can be read directly as inputs. Another group can also be read as inputs but is connected to the counter outputs; since these are open collector the lines can be used as general-purpose inputs if the counter outputs are disabled. In addition, these eight lines can be used as interrupt inputs, so interrupts from either the counter outputs or the external inputs can be generated. A third group of lines acts as outputs - they are also used to reset the input latches if necessary. Interrupts may be generated on three different conditions and may be fed to the PC's IRQ2, 3, 4, 5 and 7 interrupt lines. These conditions are that either any one or more inputs are high, or that any one or more inputs are low, or that all inputs are low. Interrupts can also be disabled. Any of the interrupt generating conditions or the interrupt disable condition, may be selected by software. A 50-way D-type connector is used to connect to the PCPIC. This allows a ribbon-cable to connect to individual cable connectors or to other boards which either modify the signal in some way or contain other types of connectors. These are called signal-conditioning boards. In an industrial environment there are many signals which it is unsafe to let into your PC. Examples are signals at high voltage such as mains, or signals with a lot of superimposed noise. This latter category includes most signals that exist in a factory. Another potential problem is that the PC may not be able to supply enough power to drive some equipment directly. Also the signals may be on cables which cannot be physically connected to the PC because they are just too big and cumbersome. The Arcom signal-conditioning system was designed to solve these problems. In essence the idea is extremely simple. All Arcom digital I/O boards have a standardised connection to a 50-way ribbon cable. TTL-level signals (together with +5V, +12V and -12V) are used Page 6

7 J230 PCPIC on this cable. The cable connects one digital I/O board to one or more signal-conditioning boards. These have a 50-way ribbon-cable connector at one end and a heavy-duty connector at the other. The heavy-duty connector can plug into a terminator mounted in a rack; the terminator can have screw terminals. A wide range of signal-conditioning boards is manufactured by Arcom (and other manufacturers). Many functions are available - optoisolation, relay outputs, Darlington and FET drivers, switch and keyboard inputs are just a few of them. It is vitally important to be able to do some form of self-test with industrial equipment. The PCPIC contains many features to assist in this. At the lowest level the PCPIC has two light-emitting diodes (LEDs). These are intended for use on initial installation, since they will not usually be visible inside the PC. The red LED flashes each time the board is accessed. This is useful to check that the board is at the correct address. The green LED can be switched on by a user program. This can be used in a power-on test routine to indicate to a technician that the board has passed. In addition, the PCPIC has an identifier code at a fixed location in the I/O map. This can be used to identify a board at a particular PCbus I/O location. The code for the PCPIC is 0C (hexadecimal) (12 decimal). What to do Next If you want to see something happening as soon as possible, turn to Section 3 for information on how to install the PCPIC in your PC. When you have installed it, run the driver software as described in Section 4. If you want to know more about how the PCPIC works, Section 5 contains details of the circuitry. If you are going to be programming the PCPIC, Section 2 has information on the I/O map. In all cases, Section 3 contains much useful information. NOTE: All addresses and data values in hexadecimal in this manual are followed by the letter H. Page 7

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9 J230 PCPIC Section 2. The PCPIC I/O Map The I/O Pointer Scheme How the PCPIC Appears in PCbus I/O Space There is a serious shortage of I/O space in most PCs. This can be a real limitation if I/O boards have lots of functions and hence lots of registers, like the PCPIC. The I/O pointer scheme used on the PCPIC and other Arcom PCbus boards solves this problem. In outline, to access a register on the PCPIC you must first set up a pointer to it by writing a byte to the 'base address' of the PCPIC. After that, you can read from and write to the register that is pointed to, by accessing the byte at the base address + 1. The base address is set up on the address Links LKA1 - LKA9. Given that the pointer value is a byte, there are 256 possible registers on a PCPIC. Obviously, not all of them are actually used. In fact, on most boards very few of them are used, but the possibilities for expansion are there. In order to allow standardisation of software some register addresses have been defined for all Arcom PCbus I/O boards. In particular, the top half of the 256 byte space has been defined as 'special function' register space, and the bottom half as 'I/O' register space. The special function registers are mostly devoted to self-test, checking, security and diagnostics. The I/O registers are the ones which the board is there for: in this case input/output and interrupt functions. The next two sub-sections describe the register allocations in detail. The PCPIC occupies two bytes in PCbus I/O space. They start on an even byte boundary. The lower byte contains the register pointer value and can only be written to. The upper byte contains the data register and can be read from or written to. The address Links LKA1 - LKA9 define where these two bytes are in PCbus I/O space. The links set the address of the lower of the two bytes (the base address); the upper byte address is one up from the base address. Another way of saying this is that the board can only be addressed at even byte boundaries and takes two consecutive bytes of I/O space. The address lines are designated A0 to A9 with A0 being the least significant and A9 being the most significant. The address links LKA1 to LKA9 are associated to address lines A1 to A9 respectively. To decode a valid board address a comparison is made between A1 - A9 and LKA1 - LKA9. LKA9 LKA8 LKA7 LKA6 LKA5 LKA4 LKA3 LKA2 LKA1 A9 A8 A7 A6 A5 A4 A3 A2 LKA1 A Page 9

10 J230 PCPIC The Registers on the PCPIC Therefore with LK7 and LK8 set, a valid board address is decoded when lines A7 and A8 are high and all the rest are low.the diagram shows a binary number of: this is not exactly convenient to use so it is usually converted to hexadecimal, in this case 180h. To do this each line is given weighting as follows: A9 A8 A7 A6 A5 A4 A3 A2 A1 A If we total the values for the high bits we can see where the 180H comes from. For example if we wanted to address the board at 192H this would become: A9 A8 A7 A6 A5 A4 A3 A2 A1 A and we would set links LK1, LK4, LK7 and LK8. Since most boards occupy more than one byte of address space, the lower address lines do not have associated links. This should be taken into account when choosing base addresses for the board. The problem comes in finding what to set the links to. Many PCs are not supplied with any information about what I/O devices are already installed at particular addresses. There are several ways round this. Firstly, try running the board at address 180H(see Section 3 for installation information). This is often unused. If you can't get any information from the PC manufacturer, run a program like Quarterdeck's Manifest, which makes a reasonable attempt to discover the addresses of common peripherals. Finally, see Section 3 for fault-finding information. The following table shows the I/O registers on the PCPIC. Pointer Value Register Name Read/Write Comments 13H CLINT W Clear interrupts 13H RINT R Read interrupt status 12H BCONT W Board control register (IC9) 11H G2IN R Group 2 inputs (IC3) 10H G1IN R Group 1 inputs (IC2) 0DH TRIGTB W Triggers timebase gate 0CH G3OUT W Group 3 outputs (IC13) 0BH IC24C R/W IC24 control register 0AH C7 R/W IC24 counter 2 - PCPIC counter 7 09 C6 R/W IC24 counter 1 - PCPIC counter 6 08 C5 R/W IC24 counter 0 - PCPIC counter 5 07 IC23C R/W IC23 control register 06 C4 R/W IC23 counter 2 - PCPIC counter 4 05 C3 R/W IC23 counter 1 - PCPIC counter 3 04 C2 R/W IC23 counter 0 - PCPIC counter 2 03 IC22C R/W IC22 control register 02 C1 R/W IC22 counter 2 - PCPIC counter 1 01 C0 R/W IC22 counter 1 - PCPIC counter 0 00 TB R/W IC22 counter 0 - timebase Page 10

11 J230 PCPIC The following table shows the special function registers on the PCPIC Pointer Value Register Name Read/Write Comments 81H Board Ident R Reading this should always give a value of OCH for the PCPIC 80H User LED W Writing 01 switches the green LED on. Writing 00 switches it off. How to Write to the Registers Counter Registers It is useful to remember that the pointer register only needs to be written to once if only one register is read or written. This means that I/O can then be done with byte reads and writes. However, if your program is continually changing registers it must write a new pointer value each times it accesses a new register. This can be done by writing a pair of bytes as a word, because the CPU in a PC does word writes to the bus (which is one byte wide) by writing the lower byte first, thus setting up the pointer register first. For example, to initialise a counter two bytes must be sent to the count register. It is not necessary to change the pointer after each write. However, when another channel is initialised a new pointer must be written, because the registers for that channel are at a different addresses. The sub-section A Quick Installation Test shows the basics of how to write to the control register. The PCPIC has a large number of I/O registers. Twelve of them are contained in the three 8254 counter chips, IC22, 23 and 24. The rest control the operation of the board. Each counter chip has four registers. Three of them are the count registers for the three counters and the fourth is the control register. In the I/O register table above they are referred to as counter 0, 1, 2 and control register. There are many ways to program an 8254 counter, and for a detailed discussion you should read the full manufacturer's data sheets, available from most distributors. In addition there are explanations of programming the 8253 counter in many books about the PC, because the 8253 is used on the PC motherboard - the 8254 is compatible with the 8253 but has a few additional features and can count at higher rates. In the following explanation we present a simplified description of programming the It is important to note that the counters are down counters. They start from the count which you have programmed into the registers and count down. You can read the count value at any time, but if you read it directly Page 11

12 J230 PCPIC make sure that the counter is not counting at the time - if it is, you may read one byte from one count and the second byte from a different count, possibly leading to serious errors. One way to avoid this is to use the count latch command, which takes a snapshot of a counter's contents. You must then read both bytes of the counter register. Another way is to use the multiple latch command, which can latch the count and status of all the counters in the chip. The 8254 can work in six different modes. Each counter in the chip is independent of the others, so each can be set up in a different mode. The control register defines the mode (and other features) and it must be programmed before the counter is used. The format of the control register is as follows. Bit Name Function Comments 7 SC1 select counter These bits select which counter to program 6 SC0 select counter 10 = counter 2, 01= counter 1, 00 = counter 0. If both these bits are high, this is a multiple latch command (See below). 5 RWM1 read/write method These two bits select how counter values are read and written. 4 RWM0 read/write method Use 11= lower byte then higher. If these two bits and all the less-significant ones are 0 ( and it s not a multiple latch command) this is a count latch command which latches the selected counter so that its count can be read while it is still counting CM2 CM1 CM0 BCD counter mode counter mode counter mode These three bits set up the counter mode. For example, 101 = mode 5, 011 = mode 3. If this bit is high the counter is a 4 digit BCd counter. If low it is a 16-bit binary counter. Use the later. The count latch command is quite straightforward. The multiple latch command has a different command word format, as follows: Bit Name Function Comments 7 SC1 Always 1. High in a multiple latch 6 SC0 Always 1. High in a multiple latch 5 COUNT Latch count This bit selects if counts are to be latched. 0 = latch counts. 1 = do not 4 STATUS Latch status This bit selects if counter status data are to be latched. 0 = latch status. 1 = do not 3 C2 counter 2 1 = select counter 2. 0 = do not. 2 C1 counter 1 1 = select counter 1. 0 = do not. 1 C0 counter 0 1 = select counter 0. 0 = do not. 0 this bit is always 0 After issuing a multiple latch command you must read the data back. If you only latched status, you only need to read one byte for each counter latched. If you latched counts you must read two bytes (lower then upper). If you latched both then you must read three bytes back for each counter selected. In this case the status is the first of the three. The format of the count data is simply the two count bytes. The format of the status is as follows: Page 12

13 J230 PCPIC Bit Name Function Comments 7 OUTPUT state of output 1 = output pin high, 0 = output pin low 6 NULL Valid count data 0 = counter data valid (count has been clocked from count register into actual counter). 1 = not valid. 4/5 RWM1 read/write method These two bits show how counter values are read and written. They should be 11 = lower byte then upper CM2 CM1 CM0 counter mode counter mode counter mode These three bits show the counter mode. For example, 101 = mode 5, 011 = mode 3 0 BCD If this bit is high the counter is a 4 digit BCD counter. If low it is a 16-bit binary counter. It should be the latter. Counter Modes For example, to set up counter 5 (wire 8 on the ribbon cable) to count down from 515 (decimal) in mode 2 using binary counting we do the following (assuming a board address of 180). Write 0BH to 180H. This sets up the pointer to IC24's control register. Counter 5 is IC24's counter 0. Write 34H to 181H. This writes the bit pattern into IC24's control register. Check this against the register format above. Write 08 to 180H. This sets up the pointer to IC24's counter 0 Write 3 to 181H. When 515 is turned into a 16-bit number the lower byte is 3 and the upper is 2. We are writing both these bytes into the counter in the order lower, upper. Write 2 to 181H. Write the upper byte. Note that the sub-section on how to write to the registers contains more information about how the pointer scheme on the PCPIC works. Each counter is made to operate in a particular mode by writing to the control register. The modes are as follows:- Mode 0: Interrupt on end of count. The output changes from low to high when the end of count is reached. The gate enables (when high) or disables the count. Mode 1: Gate retriggerable one-shot. A low-level pulse is output when the gate input is triggered (a trigger is a low-to-high transition on the gate input). Mode 2: Rate generator. The output line goes low for one clock period when the count reaches The counter operates as a frequency divider. Gate high enables. Page 13

14 J230 PCPIC Mode 3: Square wave generator. As mode 2, but the duty cycle is 50%. Mode 4: Software triggered strobe. The output goes low for one clock when the counter has counted down. Gate high enables. If gate is high the count starts from when the second count byte is written. Mode 5: Hardware triggered strobe. As mode 4, but the counter starts when the gate input is triggered. Other Registers Several registers control the operation and facilities on the PCPIC. G3OUT. Pointer value OCH Writing to this register affects outputs on group 3 of the D50 connector PL1. Writing a 1 makes an output line active-low. Writing a 0 allows it to be pulled up to +5V. This register is also used to clear the start-stop gate input flip-flops. TRIGTB. Pointer value 0DH Writing to this register creates a short trigger pulse on the timebase counter's gate. This is useful in modes 1 and 5. For example in mode 1 you may want the timebase output to open the gate to other counters for a fixed length of time. This mode is triggered by a short pulse on the timebase gate. G1IN. Pointer value 10H. Reading this gives the state of the inputs on group 1 of the D50 connector. These inputs are also connected to the interrupt control PAL IC20 and the outputs of the counters. To use them as inputs the counter outputs must be set low, because the counters are connected to inverting open-collector buffers which drive the output pins. G2IN. Pointer value 11H Reading this gives the state of the inputs on group 2 of the D50 connector. These inputs are also connected to the 'open gate' side of the start-stop flip-flops, but are not connected to any outputs, so may be read at any time. BCONT. Pointer value 12H. This is the board control register, and the correct byte must be written to it in order to set the board into the correct configuration. It controls three things - how the lower (less significant) four counters are connected, how the upper (more significant) four counters are connected, and what happens about interrupts. Three bits are used for each of the sets of counters and two bits for the interrupts, making eight bits in all. Page 14

15 J230 PCPIC The register bits are arranged as follows: Bit Name Comments 7 C2U Counter control bit 2 for the upper four counters 6 C1U Counter control bit 1 for the upper four counters 5 C0U Counter control bit 0 for the upper four counters 4 C2L Counter control bit 2 for the lower four counters 3 C1L Counter control bit 1 for the lower four counters 2 C0L Counter control bit 0 for the lower four counters 1 IS1 Interrupt select bit 1 0 IS0 Interrupt select bit 0 The counter control bits perform the following functions: Bit 210 Comments 111 Timers with start inputs on group 2 and stop inputs on group Counters with start inputs on group 2 and stop inputs on group 3 Count inputs are on group Timers with enable inputs on group Counters with enable inputs on group 2 Count inputs are on group Free-running timers Frequency inputs on group 0 Reset the start-stop flip-flops Free-running counters, inputs on group 0 The interrupt select bits perform the following functions: Bit Comments IS1 IS0 1 1 Interrupt on timer Interrupt if one or more input is high Interrupt if one or more input is low 0 0 Interrupt if all inputs are low The interrupt inputs are connected directly to group 1 pins on the D50 connector and via inverting open-collector buffers to the counter outputs. This means that if you are programming the counters to produce interrupts you must remember that the counter outputs are inverted before being presented to the interrupt controller. The other point to note is that a high counter output will prevent the corresponding group 1 input from being used as an interrupt input. If you wish to use a group 1 line as an input you must ensure that its corresponding counter output is low. One simple way to do this is to set the counter up in mode 0 and only write one of the two counter bytes. Page 15

16 J230 PCPIC RINT. Pointer value 13H This register lets you read the interrupt status. Bit 7 if high says an interrupt has occurred. Bits 2, 1 and 0 contain the priority-encoded value of the group 1 input which produced the interrupt. For example, if group 1 bit 2 and group 1 bit 5 both created an interrupt, this register will contain the value 85(hex), because the group 1 bit 5 input is a higher priority than the bit 2 input. You can, of course, read all the inputs anyway from the G1IN register; the purpose of the RINT register is to capture a transient interrupt input. The LKN1-5 interrupt link (LK1) does not have to be connected. If it is not, you can still read and clear the RINT and CLINT registers but the PC will not receive any interrupts. CLINT. Pointer value 13H Writing any value to this register clears bit 7 of the RINT register ready for the next interrupt. Page 16

17 J230 PCPIC Section 3. Using the PCPIC Installing the PCPIC The PCPIC contains CMOS circuitry and can be damaged by static electricity, as can your PC. When installing, DO NOT touch the gold edge fingers, but DO touch a metal part of your PC before picking up the PCPIC. DO NOT place the PCPIC onto plastic surfaces, particularly polystyrene or polythene. The mechanical part of installation is quite simple. In most cases it involves switching your PC off, taking its cover off, finding a spare 8-bit I/O slot and inserting the PCPIC into it. However, some PCs have different ways of doing this, so you must read your PC manual and follow its instructions. Initially we suggest that you do not use interrupts, so remove the IRQ link. Set the address links to 180 and power your PC up. Watch the LEDs on the PCPIC while it powers up. You may see the red LED flash once. This simply means that the BIOS startup program in your PC is checking through I/O space to see if any boards are there, and is nothing to worry about. On the other hand, if your PC fails to boot or the red LED flashes continuously, you will need to change the PCPIC base address (see Addresses below for suggestions). If your PC does fail to boot up, power down, remove the PCPIC and power up again to prove that the problem lies with the PCPIC rather than some disturbance created by your installation procedure, such as a loosened cable connector, for example. Addresses Although PCs differ in their available I/O address space, some generalisations are possible. There is usually space between 100H and 1FFH. Addresses 300H to 31FH are (notionally) assigned to an I/O prototyping card, so if you don't have one these are also free. Avoid addresses below 100H. Remember that many PCs 'wrap' addresses above 3FFH, so that 400H is treated as 000H, which won't work. It is not usually necessary to remove the PCPIC from the PC in order to change the address. Unless your PC is very cramped internally it is possible to adjust the address links to change address with the PCPIC still installed. Installing Multiple PCPICs This is just like installing a single one, except that they must all be installed at different addresses. The most obvious scheme is to install them at consecutive addresses, remembering that each PCPIC Page 17

18 J230 PCPIC takes up two bytes of I/O space. This is also what the Arcom software drivers expect. For example, install the first one at 180H, the second at 182H and so on. If you are installing more than one type of PCbus I/O board it makes sense to keep all boards of each type at consecutive addresses. Don't forget that other boards may take up more than two I/O address locations. If you are going to use interrupts you have two choices. Either all boards can share the same interrupt line or you can jumper one board to IRQ2 and one to IRQ3 for example. More of this later. A Quick Installation Test It is very easy to test the PCPIC with the DEBUG program to show that it is at the address you thought. Assume that the address is 180 H. Run the DEBUG program by typing DEBUG At the prompt, type o The red LED should flash once, showing that you have accessed the PCPIC. In fact, this command has made the pointer point to the green (user) LED register. To switch the green LED on, type o and to switch it off, type o To exit from DEBUG type q Links Link Position Diagram Page 18

19 J230 PCPIC There are three functions defined by links on the PCPIC: where the interrupts go to on the PC, what the timebase clock is, and the address of the board The links are defined by pushing little blue jumpers onto pairs of pins. Link 1. Where the interrupts go to on the PC This is a group of five pairs of pins just above the PCbus connector. The jumper must be inserted horizontally, which means that there are six possible situations (including no jumper inserted). LKN1 - IRQ2 LKN2 - IRQ3 LKN3 - IRQ4 LKN4 - IRQ5 LKN5 - IRQ7 No jumper means that the PCPIC cannot generate any interrupts. If you intend to use the Arcom driver software it may be necessary to insert a jumper into one of these link positions. See the section on driver software. We recommend that you do not insert a jumper into the IRQ links. Change this if you intend to use interrupts and are experienced at writing PC interrupt-handling software, or possibly if you are using the Arcom drivers. Link 2. Timebase clock This is a group of three pins in the centre left of the board. The jumpers are also inserted horizontally, and there are two possible positions, labelled A and B. Link 1A feeds a 1MHz clock into the timebase counter, and link 1B feeds a 25kHz clock into the timebase counter. Connections Connections to the board are made by a 50-way D type connector. It is usual to use a ribbon-cable (insulation displacement or IDC) connector to plug into this, so that all 50 wires are connected at once. This point is mentioned because there is some confusion about how 50-way D connector pins are numbered. Before IDC 50-way D connectors became popular the conventional numbering was to number the pins incrementing parallel to the long edge of the connector. This number is often moulded into the plastic next to each pin. Ribbon cables, however, are numbered sequentially from the stripe at one edge. This is not compatible for mechanical reasons with the original D numbering system. Because most people will use ribbon cables with this board we have Page 19

20 J230 PCPIC given connection details in terms of the ribbon-cable pins that will be connected when an IDC 50-way D connector is plugged in. They are referred to as RCx where x is a number between 1 and 50. For ease of reference the corresponding D connector pins are also shown on the circuit diagram and in Appendix B. Digital I/O The PCPIC can be used for simple digital I/O. You can read the state of the inputs on groups 1 and 2 of the D50 connector by writing 10H to the pointer register at 180H and reading the value at 181H (for group 1), or writing 11H to 180H and reading 181H for group 2. The group 1 inputs are also connected to the counter outputs, however, and you must ensure that the counter output is low, otherwise it may force the input to be low (remember that the counter output buffer is inverting). One way to do this is to set the counter into mode 0 and only write one of the counter bytes. For counter 0, for example, write 03 to 180H to set up the pointer, then write 70H to put IC23's counter 1 (the PCPIC's counter 0, since IC23's counter 0 is used for the timebase) into mode 0. Write 01H to 180H to make the pointer point to IC23's counter 1, then write (say) 0 to 181H. Frequency Outputs The PCPIC can produce up to eight square-wave outputs by feeding the timebase into the counters and setting them to mode 3, as follows: Make LK1B to feed 25kHz into the timebase. Set the timebase counter to 25, to create a 1ms clock: Write 36H to pointer 3 Write 19H to pointer 0 Write 00H to pointer 0 Set the PCPIC up for free-running timers, clock via timebase: Write 6CH to pointer 12H Set a counter up (for example counter 0) as a square-wave output counter in mode 3, dividing by (say ) 100 to give a 10 Hz output: Write 76H to pointer 3 Write 64H to pointer 1 Write 00H to pointer 1 Measuring Frequency The frequency to be measured is fed into a group 0 input and the counter gate is opened for a fixed length of time; the amount by which the counter has counted down is then the number of counts in a given time, which is frequency. The gate open time is defined by Page 20

21 J230 PCPIC the timebase and its input frequency; the timebase counter is used in mode 1, triggered by a write to the TRIGTB register. In this example we assume that the input frequency is fed into input RC3 on PL1. Make LK1B to feed 25kHz into the timebase. Set the timebase counter to 250, to create a 10ms clock in mode 1: Write 32H to pointer 3 Write FAH to pointer 0 Write 00 to pointer 0 Set the PCPIC up for frequency inputs, clock via timebase: Write 48H to pointer 12H Set up (for example) counter 0 in mode 0, and write 255 to its count registers. This will count down from when the gate is opened. Write 70 H to pointer 3 Write FFH to pointer 1 Write FFH to pointer 1 Trigger the timebase by writing anything (say 0) to the TRIGTB register Write 00 to pointer 0DH Wait for 10ms. Alternatively use the multiple latch command to read the status of the timebase counter. This will allow you to read the output pin state; in mode 1 the output will be low to keep the gate open and allow counter 0 to count, so wait until it goes high: Write E2H to pointer 3 Read one byte from pointer 0 Test bit 7. If this is 0 loop by writing E2H again Once the 10ms is over you should check that at least one transition has occurred at the input pin. If you don't, it is possible that you will not detect zero frequency properly. To do this, use a multiple latch command to check the valid count bit. Write E4H to pointer 3 Read one byte from pointer 1 If bit 6 is high no counts have happened so the frequency is zero. If the frequency is not zero, read counter 0 to see how many counts have accumulated. Read the less-significant byte from pointer 1 Read the more-significant byte from pointer 1 Turn these bytes into a 16-bit value and subtract from Note Page 21

22 J230 PCPIC that some languages cannot use 16-bit integers because one bit is used for the sign. You may have to do your arithmetic in floatingpoint if this is the case. The frequency in khz is the number of counts in 10 ms divided by 10. This timebase value will overflow at input frequencies above 6.5MHz. Counting Counting is much simpler than measuring frequency. There is no timebase to set up and several count modes are possible. The PCPIC has three ways of gating counters - not at all (PCPIC counter control bits 000), with one gate input per counter on group 2 (PCPIC counter control bits 100), and with a start count input per counter on group 2 and a stop count input per counter on group 3 (PCPIC counter control bits 110). The start and stop inputs are active-low, and are pulled high with resistors when unconnected. If you are using the start-stop method note that the start and stop inputs are setting and resetting flip-flops. In other words pulling a group 2 input (for example wire 23 of the ribbon-cable) low momentarily opens the counter gate and leaves it open until the flip-flop is reset. There are three ways to reset the flip-flop. One is to pull the corresponding group 3 input low with an external signal (in this case on wire 33 on the ribbon-cable), and another is to pull it low by writing a 1 bit to the corresponding group 3 output. These outputs are connected to the latch at pointer 0CH by inverting buffers. By the same token you must ensure that the group 3 outputs are high (that is, you have written 0 to them) if you wish to use inputs on group 3 to reset the flip-flops. The third way is to write 001(binary) to the counter control bits, then rewrite the counter control bits to put the counters back into the active mode.because the flip-flops and the group 3 outputs power-up in a random state it is good practice to reset them before use. The following example shows how to count pulses on wire 3 of the ribbon- cable for a time defined as the time between wire 23 going low briefly and wire 33 going low. Write D8H to pointer 12H to set the board control register Write 70H to pointer 3 to put counter 0 into mode 0 Write FFH to pointer 1 to define the less-significant count byte an stop the counter Write 01 to pointer 0CH to reset the input flip-flop Write 00 to pointer 0CH to enable the input flip-flop Write FFHto pointer 1 to define the more-significant count byte and enable the counter Wire 23 goes low then high, then wire 33 goes low then high Check for a null count, as described on the previous page, then read counter 0 to see how many counts have accumulated Page 22

23 J230 PCPIC Read the less-significant byte from pointer 1 Read the more-significant byte from pointer 1 Turn these bytes into a 16-bit value and subtract from This example shows how to count pulses on wire 3 of the ribboncable, with no gating. Write 00H to pointer 12H to set the board control register Write 70H to pointer 3 to put counter 0 into mode 0 Write FFH to pointer 1 to define the less-significant count byte and stop the counter Write FFH to pointer 1 to define the more-significant count byte and enable the counter Read counter 0 to see how many counts have accumulated. - You may wish to check for a null count. Read the less-significant byte from pointer 1 Read the more-significant byte from pointer 1 Turn these bytes into a 16-bit value and subtract from Measuring Time Measuring time involves opening the counter gate with your input signal(s) while feeding a known frequency into the counter clock input. The known frequency comes from the timebase. As with counting, there are three sorts of timing measurement - ungated (where the counter is free-running), with an enable input per counter and with a start and a stop input per counter. The enable/start inputs are on group 2 and the stop inputs are on group 3. The flip-flops they control can be reset with the group 3 output. The following example shows how to measure the time between wire 23 on the ribbon-cable going low briefly and wire 33 going low, using a 1ms timebase. Write FCH to pointer 12H to set the board control register Make LK1B to feed 25kHz into the timebase. Set the timebase counter to 25, to create a 1ms clock in mode 3 Write 36H to pointer 3 Write 19H to pointer 0 Write 0 to pointer 0 Write 70H to pointer 3 to put counter 0 into mode 0 Write FFH to pointer 1 to define the less-significant count byte and stop the counter Write 01 to pointer 0CH to reset the input flip-flop Write 00 to pointer 0CH to enable the input flip-flop Write FFH to pointer 1 to define the more-significant count byte Page 23

24 J230 PCPIC and enable the counter Wire 23 goes low then high, then wire 33 goes low then high Read counter 0 to see how many counts have accumulated. - You may wish to check for a null count. Read the less-significant byte from pointer 1 Read the more-significant byte from pointer 1 Turn these bytes into a 16-bit value and subtract from The result is the number of milliseconds. This example shows how to measure the time that wire 23 of the ribbon-cable is active (low). Write B4H to pointer 12H to set the board control register Make LK1B to feed 25kHz into the timebase. Set the timebase counter to 25, to create a 1ms clock in mode 3 Write 36H to pointer 3 Write 19H to pointer 0 Write 00 to pointer 0 Write 70H to pointer 3 to put counter 0 into mode 0 Write FFH to pointer 1 to define the less-significant count byte and stop the counter Write FFH to pointer 1 to define the more-significant count byte and enable the counter Wire 23 goes low then high Read counter 0 to see how many counts have accumulated. - You may wish to check for a null count. Read the less-significant byte from pointer 1 Read the more-significant byte from pointer 1 Turn these bytes into a 16-bit value and subtract from The result is the number of milliseconds. Page 24

25 J230 PCPIC Interrupts Most interrupt lines on the PCbus are already taken up by standard peripherals - IRQ2, IRQ3, IRQ4, IRQ5 and IRQ7 can be driven by the PCPIC There are eight interrupt inputs on the PCPIC. They are wired to the group 1 inputs; the counter outputs are also inverted then wired to these inputs, so the counters can generate inputs as well. The counter output buffers are open-collector, so if a counter output is low, the buffer is disabled and the group 1 inputs can then trigger interrupts if they go low. The interrupts are controlled by the bottom two bits of the board control register at pointer 0CH. The register description has details of what the bits do. It is possible to use the interrupt facility to detect short active-low pulses on group 1 without using PC interrupts. If the IRQ links are not jumpered at all no interrupts will be passed on to the PC, but you can still inspect and clear the RINT and CLINT registers. Fault finding As described earlier, there are several diagnostic aids on the PCPIC. Firstly check that the red LED lights when (and only when) your program is accessing the board. If it doesn't, it is likely that the address your program is writing is not the one that the links are set to. If this works, check that you can turn the green LED on and off by writing to its register. Try reading the board identification. If this is not correct but the LEDs have been working correctly it is possible that there is another board at the same address. Page 25

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27 J230 PCPIC Section 4. Software As you will probably have noticed from the examples using DEBUG, it is easy to prove that the board is in the system at the right address. However, the PCPIC often requires quite a few initialisation bytes and they must be sent in a particular order. To help you to get started, a disk with example software is supplied. In order to keep this as up to date as possible, files on the disk describe its contents. The file READ.ME is the first one you should look at. It contains information on the disk organisation. You can either inspect it on your screen by typing TYPE A:READ ME (If you are from reading from disk A), or print it to a printer. Your DOS manual has information about the various ways of doing this. Page 27

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29 J230 PCPIC Section 5. Circuit Description The board address is selected by IC11, an 8-bit comparator, and part of IC21. This IC, a PAL, also takes in various control signals buffered by IC16. It generates the enable signal for IC4, the data bus buffer, and strobe signals for IC25, which then decode pointer addresses for the counters and registers. It also generates strobe signals for IC26 and IC27, which holds the board identification, and IC24 which controls the green LED. The configuration of the I/O section is controlled by IC14, the board control register. Two bits from this go to IC20, the interrupt control PAL, and three bits go to IC15 and IC14 which are the gate control flip-flop PALs. Outputs from these PALs control IC17, which can let the timebase signal through into the counter gates. Two of the bits from IC12 also control IC19 and 18, which feed either the timebase or signals from group 0 into the counter clock inputs. IC8 are the group 1 and 2 input buffers and IC10 is the group 3 output latch. The 5MHz crystal oscillator output is fed to dividers IC28 and 29. Page 29

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31 J230 PCPIC Installation for CE Compliance To maintain compliance with the requirements of the EMC Directive (89/336/EEC), this product must be correctly installed. The PC in which the board is housed must be CE compliant as declared by the PC manufacturer. The type of external I/O cable can be chosen according to the notes below: 1. Remove the cover of the PC observing any additional instructions of the PC manufacturer. 2. Locate the board in a spare ISA slot and press gently but firmly into place. 3. Ensure that the metal bracket attached to the board is fully seated. 4. Fit the bracket clamping screw and firmly tighten this on the bracket. NOTE: Good contact of the bracket to chassis is essential. 5. Replace the cover of the OC observing any additional instructions of the PC manufacturer. Cable Emissions remain within limits for unscreened cables, including ribbon cables upto one metre in length. High speed counters are very susceptible to interference. In any noisy environment use fully screened cable, such as Arcom CAB50CE. For longer cables we recommend individually screened counter signal wires. Cable length 1Metre or less : Ribbon cable satisfactory Cable length 1M to 3M : Commercial screened cable gives the protection required. Longer cable or noisy environment : Use fully screened cable with metal backshells e.g. Arcom CAB50CE. The following standards have been applied to this product: BS EN : 1992 Generic Emissions Standard, Residential, Commercial, Light Industry BS EN : 1992 Generic Immunity Standard, Residential, Commercial, Light Industry BS EN55022: 1995 ITE Emissions, Class B, Limits and Methods. Page 31

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33 J230 PCPIC Appendix A. Specification Operating temperature Power consumption Counters Counter size Maximum input frequency Digital inputs 16 Digital outputs 8 Interrupt inputs 8 Input and output levels Configurations Connector Diagnostics Board identification byte PCbus I/O address space 0C to 55C 5V +/- 0.25V 520mA typical 9, in two sets of four plus one timebase counter 16 bits 8MHz TTL Frequency, counting and timing 50 way D socket Red and green LEDs 0C(H) 2 bytes Page 33