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1. Driving LED2 and LED3


2. General purpose I/Os (J7 pins 32 and 34)


3. SSP Port (also on on J7 pins 32 and 34), GM rev C

• The signals at J7 have 1k series resistance, which protects against signal contention during boot (current ADS boot code for all operating systems configures these GPIO lines as outputs during boot)


• The LEDs have their own electrical buffers. Once the StrongARM ports are configured as inputs, the LEDs will indicate the status of the external signal with no additional current draw.

• Where practical, use a different A/D input channel


• Compensate for the voltage divider in software by multiplying by 1.3


• Remove R264. It is located on the underside of the board at the corner by the compact flash socket. Be careful, as damage that occurs during rework is not covered under warranty. This work should only be performed at facilities that have surface-mount rework capabilities.


• Connect the A/D signal to J25.2 (bypasses the series input resistor)


• For volume production, depopulate the temperature circuit

• The steady state logic level of the input is now "high". In previous revisions, the steady state condition of this signal was logic "low".


• The circuit generates a brief pulse suitable for triggering interrupts. Polling RqOnOff will (almost) always return a logic high.

• You can use interrupts generated by the RqOnOff input to look for a "code sequence" (e.g. "press the power button three times within five seconds to turn the system off")


• As a factory option to production systems, ADS can manufacture rev. C Graphics Master systems using the no-debounce circuit from rev. B


• In production volume, ADS may be able to change the debounce circuit to better meet your application needs.

 Mode    Duplex    Receiver          Transmitter       
---------------------------------------------------------------------
 RS422    full     always on         always on
 RS422    half     optionally off    always on
                   during Tx             
 RS485    full     always on         Hi-Z when not transmitting
 RS485    half     optionally off    Hi-Z when not transmitting
                   during Tx
 J1708   (half)   (always on)      ( automatically on for "0" 
                                     bits and Hi-Z otherwise   )