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System Introduction 1-29
Recovery from power down is the opposite procedure.
• SIR (UART)
The FIR port is basically UART2. The UART operates off of a 14MHz clock. The IR port has a
DA converter. The UART2 disable control circuit is within the 87338 chip.
1. Tri-state the UART2 output pins.
2. Disable the 14MHz clock (If the floppy and the serial port are also disabled).
If the 14MHz is disabled through the National power down mode,
then all serial and floppy functions will fail.
Recovery from power down is the opposite procedure.
• Parallel port
Since there are no clock operations on the parallel port, the requirement to power down this
area of the 87338 chip are less critical. Also, if the floppy is operated through the parallel port,
the parallel port must be enabled to allow operation to continue.
1. Disable the parallel port decode.
• • PCMCIA Thermal
MD3_ATFINT# of U3(LM75 in media Board)
• Modem
Modem power enable. This pin[pin-43(SM5_MODPON#) of SMC] will control the power to all
of the modem chips. Once powered down, the modem chip set has no means of recovery
except through full software initialization.