Epson TM-T70II, Technical Reference Manual

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Functions of each connector pin
XON/XOFF
Whe n XON/XOFF co nt rol i s selec t ed, t he pr int er t ra n sm it s t he XON or XOFF s ign als as follows.
The t ra n sm i ss i o n ti m ing of XON/XOFF d i ffers, depe n d ing o n t he se tting of memory sw it ch 1-3.
Pin no. Signal name Signal direction Function
1 FG — Frame ground
2 TXD Output Transmission data
3 RXD Input Reception data
4 RTS Output Equivalent to DTR signal (pin 20)
6 DSR Input This signal indicates whether the host computer can
receive data.
SPACE indicates that the host computer can receive
data. MARK indicates that the host computer
cannot receive data.
When DTR/DSR control is selected, the printer
transmits data after confirming this signal (except if
transmitted using some ESC/POS commands).
When XON/XOFF control is selected, the printer does
not check this signal.
7 SG — Signal ground
20 DTR Output 1) When DTR/DSR control is selected, this signal
indicates whether the printer is BUSY.

SPACE status
Indicates that the printer is ready to receive data.

MARK status
Indicates that the printer is BUSY. Set BUSY conditions
with memory switch 1-3.
2) When XON/XOFF control is selected, the signal
indicates that the printer is properly connected and
ready to receive data from the host. The signal is
always SPACE, except in the following cases:

During the period from when power is turned on to
when the printer is ready to receive data.

During the self-test.
25 INT Input This signal can be used as a reset signal for the
printer. The printer is reset if the signal remains at
SPACE for a pulse width of 1 ms or more.