Figure 1-13. Handshaking For Rs-232C Interface; Table 1-10. Serial Interface Handshaking - Epson SQ-B50/2550 Technical Manual

1.3.2 RS-232C Serial Interface Specifications
Table 1-10. Serial Interface Handshaking
REV.-A
DTR Signal X-ON/OFF protocol Description
MARK X-OFF (DC3/13H) When the number of bytes remaining in the input
buffer reaches 256 or less, the signal level goes to
MARK, or an X-OFF code is sent to the host com-
puter. This indicates that the printer is not ready to
receive data.
SPACE X-ON (DC 1/11 H) When the number of bytes remaining in the input
buffer reaches 512 or more, the signal level goes
to SPACE, or an X-ON code is sent to the host
computer. This indicates that the printer is ready
to receive data.
DTR (REV) Signal
MARK
I
-1ZV) ----------------~~~~~~~
1I
11
SPASE (
+ 1ZV)
l)
512 byte Z56byte
X-ON X-OFF
byte Input Buffer Vacant Area
X-ON/X-OFF Protocol
Word Length:
Bit Rate:
Logic Level:
Figure 1-13. Handshaking for RS-232C Interface
Start bit 1
Data bits 8
Parity Odd, Even, or none
Stop bits..... 1 bit or more
300,600,1200,2400,4800, 9600, or 19200 BPS
EIA level, MARK..... logical 1 (-3 - 27 V)
SPACE....Iogical
°
(+3 - +27 V)
1-21