Epson C11C605001 - DFX 9000 B/W Dot-matrix Printer Service Manual page 29

General Description
indicates an RS-422 signal, which is SelecType.
Note 1: ( )
and "DTR" states can be selected through SelecType.
Note 2: 'US", "DSR",
Note3: Although the signaIs Rn, ~, DSR, DTR, and DCDare RS-232Clevel, theycanbe used
for RS-422 mode if selected through SelecType.
Note4: SD+, SD-:
Serial ASCII data output from the printer.
HIGH level; when SD+ voltage is higher than SD-voltage.
LOW level; when SD+ voltage is less than SD-voltage.
Logic O is "SPACE" and logic 1 is "MARK" state must be maintained between
transmitted character codes.
Serial ASCII data input from the computer.
HIGH level; when RD+ voltage is higher than RD- voltage.
LOW level; when RD+ voltage is less than RD- voltage.
Logic O is "SPACE" and logic 1 is "MARK" state must be maintained between
transmitted character codes.
Handshaking
When the vacant area for data in the input buffer drops to 256 bytes, the printer outputs an X~FF
cede or sets the DTR signal leveI to LOW, indicating that the printer cannot receive more data.
Once the vacant area for data in the buffer recovers to 5X2 bytes, the printer outputs an X-ON code
or sets the DTR flag to HIGH, indicating that the printer is again ready to receive data.
Protocol
There are two types of protocols, as listed below, and each of them can be designated by SelecType
independently.
the printer is ready to receive data, and to LOW when conditions indicate an error or that the
receiving buffer is full.
When the error is cleared and the printer returns to on-line mode, the signal returns to HIGH.
When SelecType is used to set the DTR controI
setting for DSR is OFF). X-ON/X~FF transmission is independent of the DSR state.
X-ON/X-OFF (DC1/DC3) protocol
indicates an error, and the printer warns the host to stop data transmission within 128 characters.
No further X-OFF codes are sent in response to additional data received from the host after the
X-OFF code has been sent once. The X43N (DCl) code is output after all renditions given in the
error are cleared.
When the remaining capacity of the receive buffer reaches 256 characters, X-OFF (DCl) is output
once. It is sent only once, even if there are multiple errors. The printer goes on line automatically at
power on, and outputs an X-ON code. Transmission of X~N/X-OFP codes can be defined by
1-18
OFF,
. .
Rev. A