Xerox 4235, Installation Planning Manual

Page: 71 / 148

SYSTEM CONFIGURATION
XEROX 4235 LPS INSTALLATION PLANNING GUIDE 6–5
Figure 6–2 shows a timing diagram.
Figure 6–2.
Centronics signal timing
Voltage levels
0 (zero) and +5 VDC (nominal), TTL (SN 74LS00 series).
Logic levels A high signal has a voltage in the range of +2.4 V to +5 V. It
should not exceed a peak of +5.5 V.
A low signal has a voltage in the range of 0.0 V to 0.4 V. It
should not exceed a peak negative voltage of –0.5 V.
However, received signals should be recognized as low signals
if the voltage is +0.8 V or less.
Current requirements The 4235 LPS interface requires up to –2.6 ma at +2.4 V for a
high output signal and requires up to 14 ma for a low output
signal.
Data rates
The 4235 LPS supports bursts of data that are at least 512 bytes
long at a rate of up to 100 KB per second through the
Centronics interface. The average data transfer rate is 15 KB
per second.
DataProducts 2260 interface
The DataProducts interface connector is equivalent to a 50–pin
Winchester connector. The Winchester MRA 50S D5J
connector mates with a Winchester MRAC 50P JTCH connector
using 50 1020P pins.
The main control signals are DEMAND, READY, and ONLINE.
At power–up, the DEMAND, READY, and ONLINE signals are
at logic zero. The DEMAND signal cycles from logic one to
zero for every byte received when the 4235 LPS is receiving
data. When the DEMAND signal is at logic zero, it indicates
that the 4235 cannot receive data. The READY and ONLINE