RCA CDP18S711 manual Using the Expansion Interface, Some Expansion Ideas

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I RCA COSMAC VIP Instruction Manual

A single photocell input could be provided via the buffered EF4 line. You can attach the photocell directly between the L and Z pads. Experimentally adjust the pull-up resistor on pad L for best operation. No photocell amplifier should be required to drive the COS/MOS input. An, externally supplied positive pulse- on. Pins 2_and 14 of U25,can be used as an input,byte- strobe when yow want to latch an input byte into U25. A 68 can be used to store

this input byte in RAM.

also latch high-order address bits to select external devices if desired. When using external circuits to generate DMA requests, interrupt requests, or input flag signals, isolate these signals with 1N914 diodes as shown for EF3 and EF4 in the optional parallel input/ output port logic. Refer to the User Manual for the CDPI802 COSMAC Microprocessor, MPM-201A, for specific examples of input/output attachment techniques.

Using the Expansion

Interface

The 44-pin card socket for the expansion interface pads along the back left edge of the PC board permits extensive expansion. If you expand beyond the capabilities of the power converter provided with the VIP, you will, of course, have to provide your own power supply. Output signals should only drive COS/MOS loads, and must be externally buffered with a. CD4050 or CD4049 IC to drive TTL loads. Keep any wires connected to the expansion pad signals as short as possible. Excessive stray capacitance on these signal lines can interfere with proper operation of the computer. Input signals should also be buffered with COS/MOS circuits. Refer to the. machine language programming section (Section IV) and the logic diagrams (Appendix E) to avoid conflicts with normal COSMAC VIP use of these signals. The external option terminal connections are given in Table III.

You can latch up the required high order address bits with the trailing edge of TPA when adding external memory. You must provide a Positive level on pad 19 to disable internal RAM when external RAM is addressed. The operating system will always use the highest page of internal (on-card) RAM, even when you add external RAM.

If you wish to substitute an external ROM or battery-powered COS/MOS RAM for U10, you can use the signal on pad X to select it. Remove U10 when substituting an external ROM. If you do use an external ROM for your own operating system you may no longer be able to use the CHIP-8 interpreter because it requires some of the operating system subroutines.

The expansion interface pads provide access to all CDP1802 signals so that you can add any desired external circuits.

Only 5 out of the possible 14 CDP1802 input/output instructions are used internally, so that you can externally decode the N0, N1, and N2 lines and use them with MRD to obtain the use of the remaining 9 input/output instruction codes. You can

Some Expansion Ideas

The August and September 1976 issues of Popular Electronics contain descriptions of a COSMAC ELF microcomputer using the CDP1802. These articles illustrate some input/output attachment techniques.

The following lists some things that with some exercise of your ingenuity could be added to your system at relatively low cost:

1.Manually operated photoelectric paper-tape strip reader. Only requires a tape guide and 8 photocells.

2.Scanning circuit for multiple input lines from

sensing devices using CD4515 IC.

3.Full alphanumeric keyboard.

4.Low-cost printer.

5.Multi-digit numeric display.

6.Calculator chip.

7.Individual photocells or switches.

8.Output relays to control solenoids, bells, whistles, sirens, lights, or motors.

9.Sound-generating circuits that can be controlled by program.

10.Analog-to-digital input circuits.

11.Read-Only Memory for fixed program.

12.Digital-to-analog output circuits.

13.Alpha wave monitor input to control pictures on TV or output devices.

14.Temperature- or pressure-sensing devices.

15.Computer terminal.

16.A second hex keyboard for multi-player video games.

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Contents Page VIP-311 RCA COSMAC VIP CDP18S711 Instruction ManualACKNOWLEDGMENT Contents Contents Continued What This Manual Covers 1. Getting StartedThe Power Supply 1. Getting Started What You SeeTurning It On Memory Write Using the Operating System11.COSMAC VIP Operation Tape Read Memory ReadTape Write 11.COSMAC VIP Operation Testing Your Cassette SystemBranch Instructions How to Change and Use the VariablesIII.CHIP-8Language Programming Using the Display Instructions 020C F090 020E F000 III. CHIP-8 Language Programming0200 A20A I=020A 0202 6100 V1=00 0204 6200 V2=00 0206 D125 SHOW 5MI@VlV2 0208 1208 GO 020A F090Applying CHIP-8 111. CHIP-8Language Programming Some Program Ideas25.PROGRAMMED SPOT - Introduce children to programming concepts by letting them preprogram the movements of a spot or object on the screen VIP Machine Coding IV. Machine Language ProgrammingMachine Language Programming Summed Up How the Input/Output Works V. Logic DescriptionHow Memory Is Addressed pressed. A 62 machine instruction causes the least significant 4 bits of memory byte to be latched into U13. These 4 bits are decoded to bring one of the 16 U13 output lines low. If the key that corresponds to this output line is pressed, the CDPI802 EF3 input will go low. The 4-bitcodes latched into U13 correspond to the equivalent key positions. After the program send8 a 4-bitcode to U13, it subsequently examines the EF3 line to see if the key corresponding to this code is pressed or not. In this manner, a program can determine when any specific key is pressed or can sequentially scan all keys while waiting for any one to be pressed. Key debounce delays must be provided in the program when required. A program can also cause a speaker tone to occur when a key is pressed. Only one key at a time should be pressed with this method of interfacing the keyboard V1. Expansion Considerations and Connections Using the Byte Input/OutputI RCA COSMAC VIP Instruction Manual Using the Expansion InterfaceSome Expansion Ideas Table III - External Option Terminal Connections Pin SignalV1. Expansion Considerations and Connections 2.Composing poetry or pictures with printer output No Sound VIL Troubleshooting HintsOther Problems Signal TracingLast Resorts Beeper Program Appendix A - Test and Operating DataByte Pattern for Displaying COSMAC Test Program Cassette Attachment Diagram Cassette Phase TestSignals Cassette Data Test Memory Test Program Cassette Recording GuidelinesOperating System Listing Appendix B - Operating SystemR3 = Machine Language Subroutine Program Counter Operating System Register TableOperating System Summary CHIP-8Interpreter Listing Appendix C - CHIP-8InterpreterInterpreter CHIP-8Memory MapCDP1802 Register Use for CHIP-8 Appendix C - CHIP-8Interpreter RCA COSMAC VIP Instruction Manual CHIP-8User NotesPage 1. VIP Kaleidoscope 2. VIP Video Display Drawing Game Circuits Appendix E - Logic DiagramsFig. E-5Power Supply Circuit and Byte Fig. E-1Microprocessor and Display InterfacePage Appendix E - Logic Diagrams Fig. E-2- ROM Circuits and Expansion InterfacePage Appendix E - Logic Diagrams Fig. E-4- RAM CircuitsRCA COSMAC VIP Instruction Manuel RCA COSMAC VIP Instruction Manual 1.Printed Circuit Board Layout Board Layout, Parts List, and Expansion NotesAppendix F 2.Parts List for RCA COSMAC VIP CDP18S711RCA COSMAC VIP Instruction Manual Page 2. Parts List for RCA COSMAC VIP CDP18S711 Page Resistors - Supplied 1 /4 W except as noted RCA COSMAC VIP Instruction ManualPage 3. COSMAC VIP Expansion Notes
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