RCA CDP18S711 Instruction Manual
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Contents
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V1. Expansion Considerations andConnectionsThe COSMAC VIP was designed primarily as aself-contained graphic system for home use. EnoughRAM and input/output features are provided for years ofcomputer fun without adding anything to your system. If,however, you do want to expand your system, a varietyof features have been included to make expansion aseasy and inexpensive as possible. You can easilyincrease RAM to 4096 bytes by adding U20-U23to your PC card. Use the same type or a compatible typeof RAM as used for U16-U19. You may, however,have to add a higher-current power supply whenexpanding RAM.Using the ByteInput/OutputFirst, you may wish to add some external com-puter-controlled devices such as relays, input sensingswitches, or even a low-cost printer. The printer willrequire an 8-bit parallel input or output port and some"hand-shaking" signals. One parallel input port and oneparallel output port are available on the PC card asshown in Fig. E-5 in Appendix E. These ports areprovided by U24, U25, U26, and U27 along withthe associated resistors and two IN914 diodes. The 22input/output port connection pads (A-Z) along theback right edge of the PC card are connected to astandard 44-pin card socket on the COSMAC VIP board.You can plug your external circuits or devices into thissocket. Table II gives the input/output port terminalconnections.The 8 buffered output signals(M,N,P,R,S,T,U,V) will each drive up to 2TTL loads. A 63 machine language instruction willlatch a memory byte into U24 for output. The 8 latchedoutput lines can be used to drive individual relay drivercircuits, power amplifiers, lights, battery motor drivers,etc. The23buffered Q output line (W) can be used as an outputstrobe for transferring the latched output byte to anexternal device such as a printer. The EF3 (X) and EF4(L) input fines can be used to indicate the status of anexternal device. Don't forget that EF3 is shared with thehex keyboard.Table 11 - Input/Output Port Terminal Connections(See Fig. E-5, Appendix E)Pin Signal Description |
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