3. ARCbus

ARCbus Introduction

The ARCbus is the ideal bus for low-cost, straightforward industrial control. It was developed around the signals from the Zilog Z8 microcomputer, and later extended to use Intel 8052 series microcomputers. Both these processors have on-chip BASIC interpreters, and there is an ARCbus board in each case which also has an EPROM programmer. In many cases you can develop, test and save BASIC programs entirely in EPROM, when the program is fully debugged it will run standalone from the EPROM. To make the system even more flexible, there is an ultra low cost version of each CPU board with no EPROM programming circuit and with a large prototyping area for your own chips. This means that you can test specified application circuits very quickly and cheaply, and it is worth noting that we have built many thousands of ‘custom’ boards based on initial prototypes tested in this way.

Standardisation is important with ARCbus boards, just as with STEbus. ARC50 CPU boards, for example, have the same serial I/O connector as the STEbus CPUs, the ARC50 and DIO5 boards have signal-conditioning connectors, giving access to the large range of signal-conditioning boards.

ARCbus Technical

The ARCbus is based on signals from (initially) the Zilog Z8 microcomputer. The logic levels and signals correspond to a subset of Zilog’s ZBUS. The ARCbus is an 8-bit bus with a data multiplexed onto the lower 8 address lines: the upper 8 address lines remain stable throughout the cycle. Valid address information is indicated by the rising of the AS signal, and valid data by DS. The R/W indicates read or write throughout the cycle. Interrupts may be used on some of the lines. The diagram below shows the pinout.

Note that power and ground lines are not compatible with STEbus.


ARCbus

Pin Row 
a c
 1GNDo oGND
 2+5Vo o+5V
 3 o o 
 4 o o 
 5 o o 
 6 o oRESET
 7+5Vo oGND
 8+12Vo o-12V
 9 o oBRW
10BASo oBDS
11 o o 
12 o o 
13 o o 
14 o o 
15 o o 
16 o o 
17 o o 
18 o oINTIN
19AD6o oAD7
20AD4o oAD5
21AD2o oAD3
22AD0o oAD1
23A9o oA8
24A11o oA10
25A13o oA12
26A15o oA14
27 o o 
28 o o 
29 o o 
30 o o 
31 o o 
32+5Vo o+5V

Pins not named are reserved.


Power connector
5-pin Berg

 1o5VMating connector
Berg part number
65240-005 (shell)
76357-401 (crimps)
 2oGND
 3oVSTBY
 4o-12V
 5o+12V

ARC40 Series

Microprocessor

The ARC40, ARC41 and ARC42 are based on the Zilog Z8671, an advanced single chip microcomputer specially designed for control applications. The ARC82 is similar to ARC42, except that it supplied with a Zilog Z8681. This is a minimum chip ROMless variant which does not have the on-chip BASIC/DEBUG interpreter. This means that for a more demanding application, all of available memory can be used to store a machine code program.

The features of the Z8671 include:

The Z8671 can autostart from power-up so that it executes a BASIC program stored in EPROM. The program can be developed and tested in RAM, then stored in EPROM using the EPIC EPROM programmer board.

Board Format

Single Eurocard size (160mm × 100mm) with a DIN41612 connector (which is optional with the ARC42 and ARC82).

Bus Connection

A DIN41612 connector allows access to the ARCbus and hence to the full range of Arcom’s peripheral and I/O boards. The bus is buffered by transceivers so that a large number of memory mapped I/O boards may be used in a system.

Software

Zilog's BASIC/DEBUG interpreter is powerful and fast enough for many control programming tasks. For more demanding applications, Arcom offer two Z8 Assemblers. RZ8 (supplied in EPROM) is exceptionally easy to use: it produces machine code instructions which can be tested and debugged in RAM prior to being blown into EPROM for autostart operation. XZ8 is a cross-assembler which runs on a disk-based development system using the CP/M operating system.

Documentation

A user's manual and software documentation are included, in the case of boards which use the Z8671, a BASIC/DEBUG Software Reference Manual is included as well. The Zilog Z8 Technical Manual and PLZ/ASM Assembly Language Manual are available from Arcom in addition.


ARC40

BASIC/DEBUG development computer with EPROM programmer and buffered I/O lines

The ARC40 is the easy to use development computer with Z8 BASIC/DEBUG, designed to solve your control and instrumentation problems. It will autostart in BASIC from power-up and its on-board EPROM programmer can use 2, 4, 8 or 16K EPROMs. Up to 40 I/O lines, including 16 buffered lines, are available - enough for most control applications (though more are available through a buffered interface to the ARCbus).

Features

Memory

There are three 28-pin memory sockets, one for EPROM (2,4, 8 or 16K) and two for CMOS RAM (2 or 8K). The CMOS RAM has a separate powerline to enable battery back-up. The ARC40 is usually supplied with two 2K RAMs, but 8K RAMs are now available.

Serial I/O

Two-way RS232 is available on a 5-pin connector. Four more RS232 lines are available for handshake or a software defined second RS232 port also on a 5-pin connector.

Parallel I/O

Two 8-bit ports of the Z8 provide 16 I/O lines, of which eight are bidirectional. Two may be taken up with serial I/O.

A further 24 I/O lines are provided by a PPI interface chip. Sixteen of these are buffered by TTL 24mA transceivers. These are available when EPROMs are not being programmed. The unbuffered lines from the PPI can be used to control the direction of the buffers, or the second RS232 port, or used directly.

Power Requirements

5V at 450mA, 12V at 20mA, -12V at 20mA (and for programming EPROMs, 28V to 35V at 30mA) are required. These values are reliably supplied by Arcom's PSU27 power supply unit.

How to Use the ARC40

The ARC40 can be connected to any RS232 terminal and a power supply. Enter your program in BASIC, test run it, debugging and editing as necessary. Then place a fresh EPROM in the zero insertion force socket and use the EPROM programming routine in the monitor. After programming, remove the standard monitor EPROM and replace it with the one you have just programmed. The board is now a standalone controller that will run your program automatically on power-up.

If you have specialised I/O requirements, you can use an ARC42 or ARC82, which both have on on-board prototyping area. In this case, the EPROM you have developed on the ARC40 can simply be transferred.


ARC41

Z8 BASIC/DEBUG with real time clock/calendar for control, measurement and data logging

The ARC41 is designed for data logging, real-time monitoring and control applications. The combination with CMOS battery backed RAM. The clock incorporates a power-saving sleep mode which allows the computer to switch itself off and be woken up by the real-time clock facility which reduces average power consumption to tens of microamps. The on-board reed relay can be used to switch external loads and a power failure detection circuit isolates the RAM and clock to prevent data corruption.

Memory

There are three 28-pin memory sockets, one for EPROM (2, 4, 8 or 16K) and two for CMOS RAM (2 or 8K). The RAM is powered from the on-board battery, which is charged whenever the board is externally powered-up.

Clock

The ARC41 uses the 146818 real-time clock. This has a full calendar with automatic leap-year calculation, periodic interrupts, time-of-day interrupt, and on chip CMOS RAM. The clock can drive a reed relay which switches power either to the rest of the board for sleep mode operation, or to an external load control lines to the RAM and clock can be isolated upon receipt of an external signal or if a power fail is detected.

Serial I/O

RS232 via standard D25 connector, selectable baud rates between 110 and 19200.

Parallel I/O

Two 8-bit ports of the Z8 provide 16 I/O lines, of which eight are bidirectional. Two lines may be taken up with serial I/O.

Power requirements

5V at 330mA, 12V at 20mA, -12V at 20mA are needed. In 'sleep' mode the board consumes just 20 microamps from the battery.


ARC42

Z8 BASIC DEBUG minimum-chip computer with prototyping area

The easy way to invent your own computer! The ARC42 runs in BASIC or machine code, has up to 16K of RAM and 12K of EPROM on board, serial and parallel I/O, yet takes up only half of a single Eurocard leaving you with a large plated through prototyping area on which to develop your own circuits.

It is ideal as a low-cost controller, either with your own I/O circuits on board or with the extensive range of Arcom I/O boards. In addition we offer an economical service should you wish to use larger quantities of ARC42s we can relay the circuit board to take your own I/O devices and produce the boards in quantity for you.

Features

The ARCbus connector can be installed as an option, to provide an interface with the range of Arcom I/O boards.

Technical Data

Though built on a standard 100 × 160 mm Eurocard, the ARC42 provides a generous prototyping area with plated-through holes on a 0.1" grid. In addition, there are two decoded chip-select signals, so you can use memory-mapped peripheral chips without any extra circuitry. To minimise wiring, the I/O ports and data bus of the are brought out to the prototyping area. A DIN41612 connector can easily be added to interface to the extensive ARCbus range of peripheral boards. The serial I/O is at TTL levels and RS232 or current-loop drivers can be added on the prototyping area.

How to Use the ARC40

To make the board into a standalone controller, install your program in the EPROM socket on the ARC42. You can develop programs on the ARC42 by using a bus connection to our EPIC EPROM programmer board or by using an ARC40 computer with its onboard EPROM programmer. Extra circuitry for your own I/O can easily be added to the ARC42 on the prototyping area.

Substantial cost savings can be made compared to multiple board systems by using our special design and production service for larger quantities of ARC42-based prototypes. Please contact us for more details.


ARC82

Z8681 ROMless minimum-chip computer with prototyping area

ARC82 is a prototyping computer, with the same useful features as the ARC42-but using the ROMless processor with machine code as the application language. This means that for the more demanding applications, you have the full memory available for your machine-code programs. Firmware developed on an ARC40 can be transferred to an ARC82 without difficulty.


ARC50 SERIES

The ARC50 series is based on two industry-proven concepts; Intel’s powerful 8052 CPU and Arcom’s well-supported ARCbus. The 8052 has a real-time 8K BASIC with full floating-point, scientific operands and strings. The ARCbus has a large number of low-cost I/O boards, including analogue, digital, power control, IEEE488 and video drivers. With a combination like this you can get control systems working in the shortest possible time. All you need to get started is an RS232 VDU, a power supply and an ARC50 CPU board.

Microprocessor

Intel’s 8052 with on-chip BASIC is an advanced single-chip microcomputer. It can be programmed in BASIC or assembly language, and programs can be stored in EPROM to create systems which autostart from power-up. The 8052 microcomputer has many exciting features including

Bus Connection

A standard DIN41612 a/c connector lets you access the ARCbus, Arcom’s low-cost, easy to use I/O bus, first used on the ARC40 series boards. There are many boards available, including analogue I/O (8 and 12 bits A/D and D/A), digital I/O, power control, IEEE488 interface, and video drivers. More boards are being added - the latest is a 40-line digital I/O board with a standard single-conditioning connector.

Software

The on-chip 8052AH-BASIC is designed for process control and instrumentation. It is very easy to use - entering a program into RAM, debugging and testing it and programming the EPROM for a target application need only take a few minutes. The BASIC has a number of features that make controlling hardware simple, including:

One feature that is especially useful in control systems is that interrupts can be handled in BASIC. This includes interrupts from external sources and from the internal real-time clock. Using this feature, it is easy to write multitasking BASIC programs and programs which respond rapidly to external events.


ARC50

8052 AH-BASIC development computer with EPROM programmer, real-time clock/calendar and buffered I/O.

The ARC50 packs more power into a single Eurocard than any other development computer. You can go through the complete development cycle with just this board, an RS232 terminal and a power supply. It has an 8K BASIC, massive memory capacity, EPROM programmer, battery-backed real-time clock, serial and parallel I/O and a bus connection on one board.

Features

Memory

There are four 28-pin memory sockets for two or three 8K RAMs and a 16K EPROM or two 8K RAMs and 24K EPROM. BASIC programs can be programmed into an EPROM using the on-board EPROM programming hardware and executed without removing the EPROM from its socket. Several programs can be saved into and read from one EPROM. The fast programming algorithm can be used for rapid program saving in 21V EPROMs. Serial I/O There are two RS232 serial ports. One is used for connection to the terminal - baud rates up to 9600 can be detected automatically at power-up, if required. The other port’s baud rate is set up with a couple of BASIC statements, and BASIC can use it to drive a printer. This port is for output only. 1/O can be redirected using assembly-language routines.

Parallel I/O

Parallel I/O is connected via the standard 50-way signal-conditioning connector. This connector is used on Arcom’s digital signal-conditioning boards, such as opto isolators, Darlington drivers and solid-state relays, and other manufacturers are adopting it as a standard. The ARC50 has 8 latched outputs and 8 buffered inputs at TTL levels, 4 counter/timer inputs, a programmable square-wave output and an MOS output line.

Real-time Clock

There are two real-time clocks on the ARC50. One is maintained inside the 8052 CPU, and is incremented every 5 milliseconds. BASIC statements can set, clear and generate interrupt jumps to other BASIC statements using this clock. The other real-time clock is a 146818 battery-backed clock/calendar which also has 50 bytes of internal battery-backed RAM and a power-fail protection circuit. The 146818 can interrupt at specified times, from seconds to 24 hours, can generate periodic interrupts, and has a 100-year calendar.

Power Requirements

Typically 5V at 1A, +12V at 100mA, -12V at 30mA and for programming EPROMs, 25V to 33V unregulated. Several Arcom power supplies are ideal.

How to Use the ARC50

You may find that the ARC50 has all the features you need on-board, so that no other boards are required. You then don’t require a backplane and you connect the power supply directly to the ARC50 using the 5-pin plug supplied. If you want to use other ARCbus boards as well, connect your power supply to an ARCbus backplane and plug the ARC50 into the backplane. If you wish to program EPROMs, connect the 25V supply directly to the ARC50 with the 2-pin plug supplied. Your RS232 terminal connects to 3 pins of a 10-pin connector on the ARC50. The printer may be wired to other pins on this connector. The ARC50 will cope with all the common baud rates on both terminal and printer. Once you’ve wired up the power supply and terminal, switch the power on and you are ready to start programming in BASIC. When you have entered a program, run and tested it, you can program it into an EPROM using BASIC commands, so that the ARC50 will autostart into your program on power-up. It’s as easy as that!


ARC52

8052 AH-BASIC minimum-chip computer with prototyping area

The ARC52 is the board to use for creating your own computer. You can program in BASIC or machine-code, drive an RS232 terminal and there is still room on the board for a large prototyping area with three decoded chip-selects. It is ideal for low-cost control jobs, either with your own I/O or with the well-proven ARCbus range of I/O boards.

Technical Data

The ARC52 is software compatible with the ARC50, which can be used to program EPROMs for use in the ARC52. It has a large prototyping area with chip selects, strobes, and address and data lines to connect your own chips. Serial I/O is at RS232 levels and terminal baud rates up to 9600 can be used.

Power requirements

Typically 5V at 0.3A, and +12V at less than 30mA if RS232 is used.

Features


I/O

DIO

Digital I/O with optional opto-isolators

The DIO is a low cost, superbly versatile and easy to use series of I/O boards for monitoring and for generating digital signals.

There are 24 I/O lines, which you can select in groups of eight to be TTL level inputs or outputs. When a group is selected for input, opto-isolators can be fitted so that signals referenced to floating or variable earth potentials can be reliably detected.

The boards versatility opens up a great many applications. For example, if you have a DIO2 set for eight TTL inputs, eight TTL outputs and eight opto-isolated inputs, you can scan a keyboard with up to 64 keys and detect eight limit switch closures on a remote piece equipment.

In common with all Arcom peripheral cards, DIOs are memory mapped with selectable addresses - several boards of each type can be used in a system.

Applications

Features

Arcom’s DIO is available in four versions:

Technical Data

The basic DIO has an 8255 24-line parallel I/O device connected to three -bit bidirectional buffers. Switches on the board select whether the buffers are set for input or output.

On input, the loading is one LSTTL load plus a pullup resistor. On output the drive capability is 24mA - enough for indicator lamps of LEDs. Opto-isolators can be fitted to any input port and the board is available in four versions. Version 1 (DIO1) has no opto-isolators. You may add them yourself if you wish, but we supply ex-stock the other DIO versions with eight, sixteen or twenty-four opto-isolators already fitted (versions DIO2, DIO3 and DIO4 respectively).


DIO5

The DIO5 gives ARCbus users access to the ever-expanding range of digital signal-conditioning boards. It has 40 I/O lines, of which 32 are fully buffered with 24mA drive sink and 15mA source capability. Direction and enable are software-programmable and 16 lines can be disabled at system power-up time for extra safety.

The board is memory-mapped, and several can be used in a system.

Features


IOC

InputOutput Controller

The IOC takes the strain from interfacing to real world power devices; it is a heavy-duty I/O controller and monitor of outstanding versatility.

Its so easy to use in an Arcom system, providing a full-feature controller which supplies a rugged interface to all types of mains equipment although it can switch DC equipment too, ideal for applications which require the programmable timing or sensing of remote switches, typical uses for the IOC include driving contractors, switching heaters and lamps, controlling thyristors and powering indicators.

Inputs

The IOC has eight opto-isolated inputs which may be used to monitor currents and voltages. The inputs are further protected by diodes which prevent reverse bias on the input LEDs. There is provision on the board to mount input current limiting resistors.

Outputs

Four Solid-State Relays

Rated at 400VAC 25A, with integral snubber networks for zero0voltage switching of medium-power loads.

Three opto-Isolated Triacs

Rated at 400VAC, 100mA, for switching small loads and for triggering triacs and thyristors.

Three Reed Relays

Rated at 100V,500mA, for DC and low-voltage AC switching.

Four Open-Collector Outputs

Rated at 50V, 500mA for driving relays and small indicator lamps.

Safety Features

To prevent loads switching on at power-up, the solid-state relays c and triacs must be enabled by a specific command from the computer. In addition, a master override controlled by one of the opto-isolated inputs may be installed. This may be operated manually if required.

Areas of the board which may be at mains potential are surrounded by an earthed guard ring.

Connections

The board connects to the ARCbus by DIN41612 64-way Eurocard connector. The opto-isolated inputs are connected by two 10-way ribbon cable headers and the outputs use plugin screw terminal connectors.


MVS1

Video Controller

MVS1 is the first in a range of video modules.

The video controller card drives a monitor to display 16 lines of 48 characters per line. There are 256 possible characters, which includes graphics and semigraphics as well as standard ASCII characters. Using the well-proven 40-Series of Eurocards you can now quickly put together a dedicated controller, a standalone computer or a low cost development system.

The MVS1 features:

Get in touch with Arcom for details of the complementary high resolution 5" monitor, which fits in a card cage. And for the 80-column version of the video controller card (the MVS2).


ADA1

8-bit, eight channel A/D, one channel D/A converter

Designed for low noise and high stability, the combination of A/D and D/A converters makes it particularly useful for loop control. A typical application could be to measure the temperature of a process (using a temperature to current transducer) and generate a control voltage for the heater. Or you could use the D/A as a programmable power supply and measure the response of the system with the A/D.

The ADA1 has user-definable input amplifiers, so high impedance inputs result in a low loading on sensors.

ADA1 features eight analog input channels and one analog output D/A) channel, each with a resolution of 8 bits (one part in 255). Conversion time per channel is 64 microseconds. The module is incredibly easy to incorporate into a system; you simply read consecutive memory locations for the automatically updated conversion figures. An output is equally easy.

Features


ADA12

12-bit, three-channel A/D, one-channel D/A converter

Input conversion is carried out by an ICL7109 integrating AD converter which is buffered from the digital bus and carefully shielded to give a very low input noise level, typically less than 20 microvolts.

The reference voltage is derived from the high stability reference on the AD567DA and fluctuations due to temperature drift are generally less than . The AD can use the DA outputs as reference to give a programmable gain facility. It can be run with a full-scale reading of a few tens of millivolts, enabling thermocouples to be measured directly in some applications.

The three differential input channels are multiplexed with reed relays for low offsets and robustness. Further multiplexing can be done offboard. The DA has a power op-amp capable of driving 300mA, with bipolar output ranges with a sample program written in BASIC.

ADA12 has a 12-bit AD converter with three input channels, a 12-bit DA converter and power op-amp output making it ideal for loop control applications.

Features


ADA16

12-bit, sixteen-channel AD converter

Again, input conversion uses an ICL7109 integrating A/D converter which is buffered from the digital bus and carefully shielded to give a very low input noise level - typically less than 20 microvolts.

A/D conversion with the ADA16 can be carried out with a full-scale reading of a few tens of millivolts, enabling devices like thermocouples to be measured directly.

ADA16 uses differential multiplexers to handle up to input channels ol 12-bit resolution, but no DA conversion is offered.

Both the ADA12 and ADA16 have a conversion time of just 30 milliseconds per channel.

Features

The easy to use ADA range allows you to measure and generate analogue voltages with great flexibility and accuracy. The fast ADA1 operates with a resolution of -bits; ADA12 and ADA16 have a 12-bit resolution.

Applications


Comparison Table

Board resolution A/D channels DA channels conversion time
per channel
typical accuracy
and stability
ADA1 8-bit 8 1 64 microseconds 2-bits
ADA12 12-bit 3 1 high-power 30 milliseconds 2-bits
ADA16 12-bit 16 0 30 milliseconds 2-bits

IEEE1

IEEE-488 GPIB Interface

This board brings IEEE compatibility to the Arcom range. Now you can connect your Arc computer to the widely accepted IEEE-488 standard for instrumentation. The board allows you to interface Arcom computers with all types of laboratory equipment, sensors, telemetry, test and measuring hardware, plotters, printers, programmable power supplies - as well as other computers.

The IEEE1 has a great many potential uses - here are just a few examples:

The IEEE board meets all the functional requirements for controller, talker and listener. Of the standard sixteen lines, eight are used for handshaking and control and eight carry data asynchronously in bit parallel. The Arcom IEEE1 uses the latest NEC IC and has the following capability: SH1, AH1, T5, TE5, L3, LE3, SR1, RL1, PP1, PP2, DC1, DT1, C1-C5.

In addition, it has a programmable data transfer rate. The bus drivers can be 3-state for high speed or open collector for parallel poll, with active turn-off when powered down to ensure that the bus is not loaded. The board can act as a stand-alone system controller or in conjunction with a separate system controller. The LED indicators allow you to inspect the state of the bus, a feature which can be immensely useful during development or when troubleshooting.

Arcom's IEEE board is supplied complete with programs so it can be plugged in and used immediately.