Service manual

Rev. 2.00
- 45 -
SRP-275
3-5-2 IEEE1284 Parallel Interface
Bi-directional parallel interface : In accordance with the IEEE 1284 Nibble / Byte mode
3-5-2(a) Forward Mode Specification (Compatibility mode)
Data transmission from host computer to printer : Centronics compatible
Item Description Remark
Data transmission • 8 bit parallel
Synchronization • External supplied nStrobe signals
Handshaking • nACK and Busy signals
Signal level • TTL compatible
Connector • IEEE1284 TYPE-B
3-5-2(b) Reverse Mode Specification (Nibble / Byte mode)
Data transmission from the printer to the host computer. The STATUS data transmission from the printer to
the host computer is accomplished in the Nibble or Byte mode. This mode allows data transmission from the
asynchronous printer under the control of the host computer. Data transmission in the Nibble mode are made
via the existing control lines in units of bits(Nibble). In the Byte mode, data transmission are proceeded by
making the 8-bits data lines bidirectional. Neither mode can operate at the same time as the compatibility
mode, so switching is always required.
3-5-2(c) Signal Specification (Compatibility/Nibble/Byte mode)
Pin no. Source Compatibility mode Nibble mode Byte mode
1 Host nStrobe HostClk HostClk
2 Host / Printer Data 0 (LSB) - Data 0 (LSB)
3 Host / Printer Data 1 - Data 1
4 Host / Printer Data 2 - Data 2
5 Host / Printer Data 3 - Data 3
6 Host / Printer Data 4 - Data 4
7 Host / Printer Data 5 - Data 5
8 Host / Printer Data 6 - Data 6
9 Host / Printer Data 7 (MSB) - Data 7 (MSB)
10 Printer nAck PtrClk PtrClk
11 Printer Busy PtrBusy / Data3,7 PtrBusy
12 Printer Perror AckDataReq / Data2,6 AckDataReq
13 Printer Select Xflag / Data1,5 Xflag
14 Host nAutoFd HostBusy HostBusy
15 - NC ND ND
16 - GND GND GND
17 - GND FG FG
18 Printer Logic-H Logic-H Logic-H
19~30 - GND GND GND
31 Host nInit nInit nInit
32 Printer nFault nDataAbail / nDataAvail
33 - NC ND ND
34 Printer NC ND ND
35 Printer NC ND ND
36 Host nSelectln 1284-Active 1284-Active