UPI-41A/41AH/42/42AH USER’S MANUAL
The 8295 Printer Controller is an example of an UPI
preprogrammed as a dot matrix printer interface.
Tape Cassette Controller
Figure 6-3 illustrates a digital cassette interface which
can be implemented with the UPI. Two sections of the
tape transport are controlled by the UPI: digital data/
command logic, and motor servo control.
The motor servo requires a speed reference in the form
of a monostable pulse whose width is proportional to
the desired speed. The UPI monitors a prerecorded
clock from the tape and uses its on-board interval timer
to generate the required speed reference pulses at each
clock transition.
Recorded data from the tape is supplied serially by the
data/command logic and is converted to 8-bit words by
the UPI, then transferred to the master processor. At
10 ips tape speed the UPI can easily handle the 8000
bps data rate. To record data, the UPI uses the two
input lines to the data/command logic which control
the flux direction in the recording head. The UPI also
monitors 4 status lines from the tape transport includ-
ing: end of tape, cassette inserted, busy, and write per-
mit. All control signals can be handled by the UPI’s
two I/O ports.
Universal I/O Interface
Figure 6-4 shows an I/O interface design based on the
UPI. This configuration includes 12 parallel I/O lines
and a serial (RS232C) interface for full duplex data
transfer up to 1200 baud. This type of design can be
used to interface a master processor to a broad spec-
trum of peripheral devices as well as to a serial commu-
nication channel.
PORT 1 is used strictly for I/O in this example while
PORT 2 lines provide five functions:
#
P
23
– P
20
I/O lines (bidirectional)
#
P
24
Request to send (RTS)
#
P
25
Clear to send (CTS)
#
P
26
Interrupt to master
#
P
27
Serial data out
The parallel I/O lines make use of the bidirectional
port structure of the UPI. Any line can function as an
input or output. All port lines are automatically initial-
ized to 1 by a system RESET pulse and remain latched.
An external TTL signal connected to a port line will
override the UPI’s 50 K
X
internal pull-up so that an
INPUT instruction will correctly sample the TTL sig-
nal.
231318 – 45
Figure 6-3. Tape Transport Controller
64