RabbitCore RCM2200 User's Manual

> ## Appendix D. Sample Circuits

> This appendix details several basic sample circuits that can be used with the RabbitCore RCM2200 modules.

>   • RS-232/RS-485 Serial Communication
>   • Keypad and LCD Connections
>   • Keypad and LCD Connections
>   • D/A Converter

> ### D.1 RS-232/RS-485 Serial Communication

> Figure D-1: Sample RS-232 and RS-485 Circuits

> Sample Program: PUTS.C in SAMPLES/RCM2200.

> ### D.2 Keypad and LCD Connections

> Figure D-2: Sample Keypad Connections

> Sample Program: KEYLCD.C in SAMPLES/RCM2200.

> Figure D-3: Sample LCD Connections

> Sample Program: KEYLCD.C in SAMPLES/RCM2200.

> ### D.3 External Memory

> The sample circuit can be used with an external 64K memory device. Larger SRAMs can be written to using this scheme by using other available Rabbit 2000 ports (parallel ports A to E) as address lines.

> Figure D-4: Sample External Memory Connections

> Sample Program: EXTSRAM.C in SAMPLES/RCM2200.

> ### D.4 D/A Converter

> The output will initially be 0 V to -10.05 V after the first inverting op-amp, and 0 V to +10.05 V after the second inverting op-amp. All lows produce 0 V out, FF produces 10 V out. The output can be scaled by changing the feedback resistors on the op-amps. For example, changing 5.11 kW to 2.5 kW will produce an output from 0 V to -5 V. Op-amps with a very low input offset voltage are recommended.

> Figure D-5: Sample D/A Converter Connections

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