Epson LQ-860 Technical Manual page 85

REV.-A
2.3.2.2 RC-232C Serial Interface
Operating Principles
The two handshaking methods are as follows :
flag . . . DTR (REV) signal
Status
The DTR signal is set to SPACE (+V) when the printer can accept data and is set to MARK (–V) when
the printer is in an error state or when the empty area in the input buffer reaches 256 bytes or less. In this
way, handshaking with the host is accomplished by setting the DTR signal to either SPACE or MARK.
(Refer to Figure 2-33.)
[ -v)
( +V)
RXD
[ -v)
NOTES: 1. The value of "T" veries according to the input data.
2. The word structure of the serial data is :
1 start bit + 8 data bits + parity (Odd, Even, or none) + 1 or more stop bits.
2. X-ON/X-OFF protocol . . . Sent over the TXD line
Handshaking is accomplished by sending either X-ON (IIH) or X-OFF (13H) over the TXD line to the host.
When the printer can accept data, the printer sends an X-ON code. When the printer becomes busy, it
sends, an X-OFF code to the host computer. "The X-OFF code is sent to the host when the empty area in
the printer input buffer reaches 256 bytes or less, or when the printer is in an error state (Refer to Figure
2-34.).
( + v)
[ -v)
NOTES : 1.
The value of "T" veries according to the input data.
2. The word structure of the serial data is :
1 start bit + 8 data bits -t parity (Odd, Even, or none) 1 or more stop bits,
Start
Bit
Figure 2-33. Handshaking with DTR Signal
Start
Bit
Figure 2-34. Handshaking with X-ON/X-OFF Protocol
D a t a B i t I
S t o p B i t
Parity
Bit
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[ [
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S t a r t
D a t a Bit
B i t ( X - O F F ]
2-38
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