Radio Shack TRS-80 Model 4 - Page 347

The parallel printer pin-outs and signals available are listed below.
NOTE:
If a signal name contains an asterisk ( * ), the signal is
active-low.
Signal
Function
Pin
#
STROBE*
1.5 microseconds pulse to clock
1
the data from processor to printer
DATA
0
Bit 0 (Isb) of output data byte
3
DATA 1
Bit 1 of output data byte
5
DATA 2
Bit 2 of output data byte
7
DATA 3
Bit 3 of output data byte
9
DATA 4
Bit 4 of output data byte
11
DATA 5
Bit 5 of output data byte
13
DATA 6
Bit 6 of output data byte
15
DATA 7
Bit 7 (msb) of output data byte
17
BUSY
Input to computer from printer, high
21
indicates busy
PAPER
Input to computer from printer, high
23
EMPTY
indicates no paper -
If the printer
doesn't provide this, the signal
is
forced low
BUSY*t Inverse of BUSY (Pin 2) 25
FAULT*
Input to computer from printer, low
28
indicates fault (paper empty, ribbon
out, printer off-line, and so on)
GROUND Common signal ground
2,4,6,8,10
12,14,16,
18,20,22,
24,27,31,
33
NC
Not connected or not used 19,26,29,
30,32,34
t Depending
on the kind of printer used, this signal may be called
"UNIT SELECT." See your printer manual for more information.
Communications
For hardwiring two Model 4/4P's without a modem, use Radio Shack's
RS-232C cables (cat.
no. 26-1490, -1491, -1492, -1493) and null
modem adapter (cat.
no. 26-1496).
A-43