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3600 Printer Maintenance Manual
A-8
Channels 7 and 8 These outputs control the front panel LEDs. They can be set
to high, low, or square wave outputs. The square wave output frequency is
programmable.
Channel 9 This output is reserved. It has RXD as an input for autodetection of
the serial communications parameters.
Channel 10 This is an input for the ribbon sensor. The channel detects
transitions on the input. If it does not receive a transition before it receives a
programmable number of links from channel 0, it interrupts the CPU to
indicate a ribbon failure.
Channel 11 This output generates the refresh requests for the DRAM. It
generates a low pulse at a programmable frequency and duration.
Channel 12 This is an input for the front panel switch. It detects transitions on
the input, debounces the switch, and interrupts the CPU.
Channel 13 This output generates a square wave of a programmable
frequency. It is used to set the current level for the motor driver circuit.
Channel 14 and 15 These channels are reserved to support a cutter or a wand
port.
QSM
The QSM consists of two modules, a serial peripheral interface (SPI) and serial
communications interface (SCI). The SPI is used to communicate with the A/D
converter. It takes continuous readings and stores the values in RAM for
immediate access by the CPU. The SCI is used for RS-232/RS-485
communications. Other pins are used as general purpose I/O.
Interrupt Priority Levels
The SIM module has seven IRQ pins to help facilitate external interrupts in the
3600:
• /I/ORCV, /I/OXMT, /PFAIL, and HF are available as interrupts.
• /I/ORCV and /I/OXMT are used for communications with the I/O option
interface.
• HF is used to indicate that the FIFO needs service.
• /PFAIL indicates a loss of power.
• The IRQ pins are used for general purpose I/O.
Crystal
The clock synthesizer of the MC68332 can operate from an on-chip, phase-
locked loop using an external crystal. A 32.768KHz crystal provides a reference,
allowing the processor to run at frequencies from 131KHz to 16.777MHz. The
clock synthesizer is programmed to run at 16MHz in the 3600.