Epson U375 - TM B/W Dot-matrix Printer, Technical Manual

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2-22
Host interface circuit and customer display interface
circuit
The printer has an RS-232C interface for connection to the
host computer and a customer display interface for connec-
tion to the customer display (DM-D).
The driver/receiver ICs (U2 and U3) handle level conver-
sion (TTL
÷
±
12V) for the RS-232C and customer display
interface signals.
Figure 2-43 shows device connection block diagrams illus-
trating the connections between the printer (TM), host
computer (HOST) and customer display (DM-D).
In connection (b), printing on the TM is possible by using the
pass through function of the DM-D. In connection (c), to
send data to the DM-D through the TM, the RXD signal
terminal (pin 3) of the host interface connector (CN2) on the
TM and is connected directly to the RXD signal (pin 3) of the
customer display interface connector (CN7).
Pins 6 and 25 of the interface connector carry the printer
reset signal, which is selectable by DIP switch. (Refer to
SW 7 and 8 of switch bank 2 in Table 1-10,
DIP switch bank
2.)
Then select the Seiko Epson customer display by setting
DIP switch 1 on the bank 2 to ON. When this setting is in
effect, the RTS signal which is output will be the AND of the
DTR signal from the customer display and the DTR signal
from the printer.
When neither the customer display or the printer DTR
signal is SPACE, the RTS signal is not SPACE either.
When DIP switch 1 of the bank 2 is OFF, the same signal
as the printer's DTR signal is output to the RTS signal.
See Chapter 7 for the TM-U375P host interface circuit.
Figure 2-43. Device Connection Block Diagram
CONFIDENTIAL