REV.-A
Serial Interface Control Circuit
y.-
~
x
Serial data communication between the printer and host computer is controlled by the serial interface
‘:’
board (#8 143). Other buffered serial interface boards are available.
Figure 2-30 shows
HOST
COMPUTEF
the serial data flow.
-F+F
8143
RXD
-
BUSY/RDY
DTR
TXD
TXD
d?%
t
BUSY
~,
I
DO
GA
CPU
(78 10HG)
(4B)
RXD(PC
1
)
PD7
I
PDO
TXD(PCO)
Figure 2-30.
Serial Data Flow
Sequence
1. Serial data from the host computer is input to terminal IN7 of the gate array via the optional interface
(8 143) using a start-stop system. The serial data is input in order of the start bit, data (7 or 8 bits),
and stop bits. While a byte of data is being processed, the printer is kept in the BUSY state.
2. The data input into the gate array is serially transferred from the RXOUT terminal to the
RXD
terminal
of the printer.
3. The byte of serial data input to the CPU is converted from serial to parallel in the CPU and stored
in the input buffer. The BUSY state is cleared.
4. The printer is ready to accept the next data byte.
$:-.,
;“
2-36
!,
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