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Appendix A System Interface Description
2. Parallel Centronics Interface
2.1 Interface Characteristics - Connector Pin Assignment / Signal
Definition
_______
Control Signal from the Host. Printer reads data line
*)
STROBE
(Data 1 to Data 8) when going low.
Data 1 - 8
Data lines transfer the characters from the host to
the printer. Data 8 = most significant bit.
_____
Acknowledge - Negative going pulse from the printer
*)
ACKN
indicates that the printer has received a character
and is ready for the next data transfer.
BUSY
Control signal from the printer. A high level indicates
that the printer is unable to receive any more data.
PE
Paper Empty - Control signal from the printer. This
signal goes high when paper runs out, i.e. load
upper or lower tractor, paper jam.
SELECT
Control signal from the printer. A high level indicates
that the printer is ON-LINE and ready.
LG
Logic Ground
--
not used
LG
Logic Ground
CG
Chassis Ground
VCC
+ 5 volt
SG
Signal Ground
____
Control signal from the host. Does not reset the prin-
*)
INIT
ter.
______
Control signal from the printer. A low level indicates
*)
FAULT
that the printer has been switched off, or the serial
interface is active.
LG
Logic Ground
--
not used
_________
Compatible mode (low) 1284 nibble mode (high)
SELECT IN
*)
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 buffer space is available again for least
512 characters in the interface buffer. While the printer is offline (Stop Mode)
BUSY remains active until the printer enters the online state again.
IEEE Std 1284 Nibble mode including Device ID are supported.
The maximum throughput for data transfer is 42,000 characters per second.
A-8
®
Signal Description
Pin No. Return line Direction
Pin No.
1
19
2 - 9
20 - 27
10
28
11
29
**)
12
--
13
--
14
--
15
--
16
--
17
--
18
--
19 - 20 --
31
--
32
--
33
--
34 - 35 --
36
30
Input
Input
Output
Output
Output
Output
Input
Output
Input
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