UPI-41A/41AH/42/42AH USER’S MANUAL
available to control a 16-digit, 7-segment display. The
UPI can also be programmed to recognize special com-
binations of characters such as commands, then
transfer only the decoded information to the master
processor.
Matrix Printer Interface
The matrix printer interface illustrated in Figure 6-2 is
a typical application for the UPI. The actual printer
mechanism could be any of the numerous dot-matrix
types and similar configurations can be shown for
drum, spherical head, daisy wheel or chain type print-
ers.
The bus structure shown represents a generalized, 8-bit
system bus configuration. The UPI’s three-state inter-
face port and asynchronous data buffer registers allow
it to connect directly to this type of system for efficient,
two-way data transfer.
The UPI’s two on-board I/O ports provide up to 16
input and output signals to control the printer mecha-
nism. The timer/event counter is used for generating a
timing sequence to control print head position, line
feed, carriage return, and other sequences. The on-
board program memory provides character generation
for 5 x 7, 7 x 9, or other dot matrix formats. As an
added feature a portion of the data memory can be used
as a FIFO buffer so that the master processor can send
a block of data at a high rate. The UPI can then output
characters from the buffer at a rate the printer can ac-
cept while the master processor returns to other tasks.
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Figure 6-2. Matrix Printer Controller
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