Siemens 9015 Manual De Usuario
Centronics
Interfaces
Programmer Reference Guide
U26169-J-Z716-1-7600
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Protocol description
After power-on, the
PE
signal goes to zero. The
SELECT
signal and the
FAULT
signal
become one.
Timing
The host sets the data lines (
DATA 1
-
DATA 8
) according to the character to be transferred.
After a timeout of 0.5 microseconds the host sends a
STROBE
pulse with a length of at least
0.5 microseconds. The character is stored in the printer buffer and the printer sends a
BUSY
signal to the host. When the data byte is stored completely in the printer buffer, the printer
sends a
sends a
BUSY
and an
ACKN
signal to the host.
The
ACKN
signal informs the host that a data byte has been received and that the printer is
ready to receive another character.
When the printer buffer is full, the
BUSY
signal is not reset to stop the data stream from the
host. The
BUSY
signal is reset only when at least 256 bytes are free in the printer buffer.
When the Stop button is pressed, the
BUSY
signal remains one and the
ACKN
signal is not
sent.
If at least 256 bytes are free in the printer buffer, pressing the Start button causes the
BUSY
signal to be reset and an
ACKN
signal to be sent to the host.