Star Micronics Radix User Manual page 263

c
Appendix F
I i
The Parallel Interface
i
Radix has both a parallel interface and a serial interface to
communicate with the computer that it is connected to. The oper-
ating specifications of the parallel interface are as follows:
Data transfer rate:
1,000
to
6,000
characters per second
Synchronization:
Via externally supplied STROBE pulses
Handshaking:
ACK and BUSY signals
Logic level:
Compatible with TTL level
Radix's parallel interface connects to the computer by a 36
pin connector on the back of the printer. This connector mates
with an Amphenol
57-30360
connector. The functions of the vari-
ous pins are summarized in Table F-l.
Functions of the Connector Signals
Communications between the computer and the Radix use
many of the pins of the connector. To understand how the system
of communications works we need to look at the functions of the
various signals carried by the pins of the interface connector.
Pin 1 carries the STROBE pulse signal from the computer to
the printer. This signal is normally held high by the computer.
When the computer has data ready for the printer it sets this sig-
nal to a low value for at least 0.5 microseconds. When the printer
sees this pulse on the strobe pin, it reads the data that the com-
puter supplies on pins 2 through 9. Each of these lines carries one
bit of information. A logical
"1"
is represented by a high signal
level, and a logical "0" is represented by a low signal level. The
computer must maintain these signals for a period beginning at
least
0.5
microseconds before the strobe pulse starts and continu-
ing for at least 0.5 microseconds after the strobe pulse ends.