TallyGenicom T2265, Maintenance Manual

Page: 43 / 190

2.2 Phase 2, Data transmission phase
This phase is activated even after phase 1. A string of characters is transferred from
the printer to the PC, which immediately describes the printer type, the manufacturer,
the device class and some sort of compatibility.
Procedure
– SELECTIN and AUTOFEED are set to low by the PC at the same time
– Within 35 ms the printer reacts with SELECT, ERROR, PAPEREND and DONE
set to low.
– PC transmits one Byte with a STROBE pulse and sets AUTOFEED to high
– This byte will be analyzed by the printer. If everything was ok the byte should be
04hex which means that PC is demanding the identification of the printer in
Nibble Mode. The printer agrees setting PAPEREND to low and DONE to high.
– PC answers setting AUTOFEED to low.
– Now the initial procedure starts by sending the characters. The string is built up
in a way that the first two bytes are indicating the total length of the string
(including the first two counter bytes). MSB first then LSB is transmitted followed
by the characters.
– Each byte starts by putting bits 0 - 3 to the control signals (see above).
– This Nibble (half - byte) is released setting DONE to low.
– The acknowledge of PC is done by setting AUTOFEED to high.
– As soon the printer recognizes the acknowledge DONE is put back to high.
– As a result the PC sets AUTOFEED back to low.
– Now bits 4 - 7 are sent using the signal lines.
– This Nibble (half - byte) is released setting DONE to low.
– The acknowledge of PC is done once more by setting AUTOFEED to high.
– As long as there are data to be transmitted the printer sets now PAPEREND,
ERROR, SELECT and BUSY to low and DONE once more to high.
– The acknowledge of the PC is performed by setting AUTOFEED to low.
– Now the next nibble can be sent and the procedure is repeated.
– If there are no more data to be transferred after the last Nibble (half - byte) the
printer is setting ERROR to high, SELECT, PAPEREND and BUSY to low.
– This will be release setting DONE to high.
– Now the termination of the data transmission phase is starting. The PC sets
SELECTIN signal to low.
– The printer reacts – different than in the negotiation phase - with SELECT set to
low, BUSY set to high and - after a short delay - DONE set to low.
– The printer is setting ERROR and SELECT according to the actual status in
normal Centronics mode and after that DONE back to high.
– PC reacts setting AUTOFEED to high.
– At the very end of the data transmission phase the printer sets BUSY and DONE
according to the actual state in normal Centronics mode.
– Now everything is in normal state again and the transmission of the printer
identification is completed.
32
32
35
35
36 X3
36 37
B5
4
5
CA2
VCC
2
7
3
6
1
8
2
21
21
GND
GND
C9
12
100N
R58 10K
1 2
10
10
31
31
34
34
20
20
9
9
30
30
19
19
8
8
29
29
18
18
7
7
28
28
17
17
6
6
26
26
16
16
5
5
25
25
15
15
4
4
23
23
13
13
2
2
24
24
14
14
3
3
22
22
12
12
11
11
1
1
36
EGND
G
ND
R19
CBB
2
2
2
1
1
1
F
AUL
TN
SELECTI
N
P
AR. INTERF
GND BUSYX INIT GND DONENX GND GND GND ID8 GND GND ID7 GND VCCX ID6 GND EGND ID5 GND GND ID4 GND ID3 GND AUT
OFD
ID2 ID1 GND PE SEL STROBEN
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Functional Description Electronic Functions
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