Radio Shack TRS-80 PT-210 Service Manual page 29

Carriage Return and Line Feed Motor Control
Two pulse motors are used in the printer unit. X I
-
X 4 make carriage returns, and Y1
-
Y 4 make line
CN I
Carriage
I
Retu&Motor
Figure 20.
1
Method for excitation of the carriage return and line feed motors:
When '*L" is input to the PROG terminal in accordance with an instruction from the pCPU, a motor 0x-
citation signal is output to an
1 1 0
expansion port.
Port 4 (P40
-
P431 is for carriage return signals, and port 5 tP50
-
P531 is for line feed signds.
A signal output to port
4 or port 5 is driven by a transistor and drives the applicable motor.