Specifications

E–8 Principles of Operation
RTPU; it is sixteen bits wide and is arbitrated on a cycle–by–cycle basis. The
8032 chip has its own eight bit local bus. The manner in which the CCB
implements this hardware is depicted in Figure E–5.
The 64180 IC that oversees the RTPU processor contains a Z80
microprocessor with extended memory management, two DMA controllers,
two asynchronous and one synchronous serial port, two counter timers, and
an interrupt controller.
Communicating with the Host Computer
The 64180 processor runs both the parallel and serial interfaces.
Parallel Input Parallel input data is nine bits wide, and is transferred in one
cycle from the parallel port to shared memory over the shared sixteen bit bus.
Using the internal DMA controller of the 64180 to transfer parallel data
requires some manipulation. The eight bit DMA controller in the 64180
performs either eight or sixteen bit DMA cycles, while the eight bit processor
in the 64180 performs only eight bit memory access cycles. Sixteen bit DMA
is achieved by hardware shifting of the DMA addresses one bit (effectively
multiplying the address by two and changing the DMA auto–increment from
byte to word) and by manipulating the control strobe. Software adjusts the
addresses provided to the DMA controller when it is programmed for sixteen
bit DMA. This manipulation saves both the added cost of a sixteen bit DMA
controller and the second cycle that an eight bit transfer would require.
Serial Input One of the 64180 UARTs handles serial communication with
the host. Additional modem control lines are provided in the 64180 hardware
control register.
Communicating with the Operator
The synchronous serial port in the 64180 shifts data in and out of the operator
control panel. The control register in the 64180 contains three other control
panel bits: one samples the switches, one strobes the liquid–crystal display,
and one strobes a light–emitting diode (LED) holding register.
Printing
Hammer Driver Interface The 64180 programs the dot plucker ASIC
every dot row and programs the FTIC every stroke, after which the FTIC
uses a DMA request line to control the movement of tables from EPROM to
FTIC. The second DMA controller in the 64180 performs this transfer.
Mechanism Driver Interface The paper feed controller (PFC) directs all
paper motion. During printing, it usually moves paper in response to a trigger