Star Micronics Radix User Manual page 270

256 Radix User's Manual
&wiai busy
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In the serial busy protocols, Radix uses DTR (pin
20)
and RCH
(pin
11)
to signal to the computer when it is able to accept data.
These two pins go ON when Radix is ready to accept data. In the 1
byte mode they go OFF after each character is received. In the
1
block mode they only go OFF when Radix's buffer approaches
capacity. In both cases they will stay OFF if the buffer is too full to
accept more data.
XONIXOFF
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The XONlXOFF protocol uses the ASCII characters (DCl)
and (DC3) (sometimes called XON and XOFF, respectively) to
communicate with the computer. When Radix's buffer
approaches capacity Radix will send a DC3 (ASCII 19) on TXD
(pin 2) to tell the computer that it must stop sending data. When
Radix is able to receive more data it sends a
DC1
(ASCII
17)
on
TXD. The computer can then send more data until Radix sends
another DC3.
ACK
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In the ACK protocol, Radix sends an ACK (ASCII 6) on TXD
(pin 2) each time that it is prepared to receive a byte of data.
I
Figure G-1.
Typical data byte on the serial interface.
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