2-38 Mechanism Configuration and Operating Principles Rev. A
Host interface circuit for the TM-U950
The printer has an RS-232C interface for connection to the host computer and a DM interface for
connection to the customer display (DM).
The driver/receiver ICs (U2 and U3) handle level conversion (TTL ↔ ± 12V) for the RS-232C
and customer display interface signals.
Figure 2-45 shows device connection block diagrams illustrating the connections between the
printer (TM), host computer (HOST) and customer display (DM).
In connection (b), printing on the TM is possible by using the passthrough function of the DM. In
connection (c), to send data to the DM 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 1-8, DIP switch settings.) Then select the
Seiko Epson customer display by setting DIP switch 6 on the bank 1 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.
Figure 2-47a. DIP Switch Circuit for the TM-U950P
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RM1
RM2
1
5
2
1
U10 U17
1
5
2
1
9
9
7
7
RM15
RM16
DSW1 DSW2
{ 5V
{ 5V
R80
Q21
Q19
SWSL
DSW2
6
SWCK ⁄ T19
SWCL ⁄ T21
SW1I ⁄ T8
SW2I
PB2
PB3
PB0
PB1
Gate array
CONFIDENTIAL
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