Operating phases, Parallel interface signals, 21 parallel interface signals – Compuprint 3046 Programmer Manual User Manual
Page 21
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The link protocol is mainly based on the following three phases:
• Negotiation Phase
This phase is activated always by the host, only when in compatibility mode, and defines:
- whether a bidirectional link protocol can be established.
- the handshaking mode as well as the communications mode to be used.
- the device identification, if supported.
• Communication Phase
This phase is based on well defined handshaking rules which depend upon the selected link mode.
• Termination Phase
This phase is initiated by the host and returns the interface to the compatibility mode.
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Description of the signals in monodirectional link:
Signal Name Pin N°
Source
Description
STROBE
1
HOST
Clock signal which controls data transmission with its falling edge.
ACK
10
PRINTER
Negative pulsed signal indicating that the printer has received data
and is ready to accept the next set of data. Also sent when the
printer is switched from off-line to on-line and at the end of the
initialization time. The BUSY line is always active.
DATA BIT 1
DATA BIT 2
DATA BIT 3
DATA BIT 4
DATA BIT 5
DATA BIT 6
DATA BIT 7
2
3
4
5
6
7
8
PRINTER /
HOST
Data 8 is the most significant bit. These are the data lines used by
host to transfer control code or ASCII codes.
DATA BIT 8
9
BUSY
11
PRINTER
When high, this signal indicates that the printer cannot accept data
or control codes. This signal goes high during data processing, in
test and program modes, during initialization, when the buffer is
full, and when a paper jam, paper end or paper size error occurs, in
case of a power-on reset, the reception of a STROBE signal, while
the register was not yet read, or when the INIT line is still active.
PE
12
PRINTER
When high, this signal indicates that printer is out of paper .
SELECT
13
PRINTER
When high, this signal indicates that the printer is on-line.