Appendix A System Interface Description
Appendix A System Interface Description
A-7
A-8
Additional Information
3
Parallel Centronics Interface
After Power-ON DTR and RTS are activated and the printer is ready to receive
data.
Interface Characteristics
- Connector pin assignment / signal definition
XOFF
is sent, when the interface buffer has only space left for 256 more charac-
ters.
XOFF
is sent again, at a level of 128 characters buffer space. Further
incoming data will be stored until the interface buffer is full. All data sent in
addition will get lost.
XON
is sent when the interface buffer provides space for a minimum of 512
characters.
XON/XOFF
can only be sent successfully when
CTS
and (
DSR
) is at active
state.
XOFF
will be sent immediately if local mode is entered.
XON
is sent again, if local mode is left and a minimum of 512 byte interface
buffer is available.
®
Signal Description
line Pin
Pin No.
Return
Direction
No.
_______
Control Signal from the Host.
1
19
Input
STROBE
Printer reads data line (Data 1 to Data 8) when
*)
going low.
Data 1 - 8
Data lines transfer the characters from the host to
2 - 9
20 - 27
Input
the printer. Data 8 = most significant bit.
_____
Acknowledge - Control signal from the printer. Logi-
10
28
Output
ACKN
cal 0 indicates that the printer has received a print/-
*)
control character and is ready for the next data
transfer.
BUSY
Control signal from the printer. Logical 1 indicates
11
29
Output
that the printer is unable to receive any more
data.
**)
PE
Paper Empty - Control signal from the printer. This
12
--
Output
signal goes high when paper runs out, i.e. load
upper or lower tractor, paper jam.
SELECT
Control signal from the printer. Always logical 1.
13
--
Output
Indicates that the printer is
ON-LINE
and ready.
LG
Logic Ground
14
--
--
not used
15
--
LG
Logic Ground
16
--
CG
Chassis Ground
17
--
VCC
+ 5 volt
18
--
SG
Signal Ground
19 - 30
--
____
Control signal from the host. Does not reset the
31
--
Input
INIT
printer but generates an acknowledge pulse (logical
*)
1).
______
Control signal from the printer. Always logical 1. If it
32
--
Output
FAULT
goes to logical 0 the printer has been switched off.
*)
LG
Logic Ground
33
--
--
not used
34 - 36
--
Overlined signal names indicate that the signal is true when the signal level is
*)
low.
When the interface buffer is full except for the last character,
BUSY
will not be
**)
reset.
BUSY
will be reset when space is available again for least 256 charac-
ters in the interface buffer. While the printer is offline (Stop Mode)
BUSY
remains active until the printer enters the online state again.
