Tally T2265 SprintPro, Maintenance Manual

Page: 40 / 178

3.3.3
Bidirectional
Centronics
Interface
1. Overview
This SIDM printer is equipped with a parallel Centronics interface which is located on
the main electronic pcb. The data transfer handshake (with some smaller exceptions)
has been implemented according IEEE1284 standard. Up to now (13.12.95) only the
Nibble Mode was implemented (Bytemode, ECP-Mode and EEP mode may follow
later per request). The Nibble Mode has been adapted to meet the requirements
Microsoft Windows (TM) Operating System which does a printer identification using
“Plug’n’Play”. A graphical schematic is shown in the IEEE1284 standard picture 3,
page 25 and picture 9, page 35.
2 Detailed description of data transfer in Nibble Mode
The transmission of printer identification is divided into two parts. In the first phase
there is a “negotiation” between PC and printer to activate Nibble Mode. In the
second phase there is a data transfer. At the end of each phase there is a reentry to
to the normal Centronics mode according a defined handshake procedure. The name
“Nibble Mode” in this case means that the transmission is performed in two packages
per 4 bit in direction to the PC using existing control lines (bit 0/4=Error, Bit
1/5=Select, Bit 2/6=Paper-End, Bit 3/7=Busy). All other possible modes are using the
8 standard data lines - now in the opposite direction (printer - PC)
2.1 Phase 1, Negotiation phase
Procedure
– The PC sets SELECTIN to high and at the same time AUTOFEED to low.
– The printer reacts within 35ms with SELECT, ERROR and PAPEREND to high
but DONE to low
– PC transmits one data byte to the printer with a STROBE signal and sets
AUTOFEED to high
– This byte will be analyzed by the printer. If all seems to be ok this byte should be
00hex witch means the PC likes to know whether or not the printer is supporting
Nibble Mode.
– Since the printer is able to run Nibble Mode the printer answers then with
SELECT, ERROR and PAPEREND to low. To create an interrupt at PC side,
DONE will be set to high at the end.
– Now the termination of the negotiation phase will be done by setting SELECTIN
to low.
– As a result the printer is setting SELECT and BUSY to high and after a short
delay also SELECTIN to low.
– As a reaction AUTOFEED is set to low at PC side.
– The printer is now setting ERROR and SELECT in normal Centronics mode
according the actual state and after that DONE is changed back again to high.
– PC should react then setting AUTOFEED signal to high
– As the very end of this negotiation phase the printer sets BUSY and DONE in
normal
– Centronics mode according the actual state.
– Now everything is in normal state.
Electronic Functions Functional Description
3-22