6.3 Interface Specifications
Parallel Interface
The parallel interface is based on the Centronics standard.
Specifications:
• data transfer speed: 1000 cps minimum
•synchronization: external STROBE pulse
• logic levels: TTL
_____
• handshaking: BUSY and ACK signals
•connector type: 57-30360 (AMPHENOL) or equivalent
•cable: use a shielded cable 6.6 feet (2 meters) or less in length.
When the printer is processing data, the BUSY signal is high. The printer
will not accept new data from the computer. After the processing is
completed, the BUSY signal goes low. (The BUSY signal is also high
when the printer is OFF LINE.)
When this occurs, the ACK signal goes low indicating to the computer
that the data has been processed and the printer is ready to accept more
data. This handshaking routine occurs each time a character is sent to the
printer.
BUSY SLCT
PO
ERROR
ON LINE
LOW HIGH
LOW
HIGH
OFF LINE
HIGH LOW
LOW
LOW
PAPER OUT
HIGH
LOW
HIGH
LOW
Table 6.1 Printer status signals
Specifications 6-7
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