Fujitsu C145-C037-01EN, Product Description

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5-11
T2 T1 T3 T5 T6 (*)
T4
(*)
Data 1 to 8
Data Strobe
Busy
* The values of T4 and T6 are assumed that the host uses ITTL for
its input circuits.
T1, T2, T3 > 0.5
µ
s
T4 < 0.5
µ
s (*)
T5, T7 = 0
µ
s
T6 = 0.5
µ
s (*)
Acknowledge
T7
Figure 5.8a Data transmission timing (compatible mode)
5.3.3 Data transmission timing
The PrintPartner 20W uses a bi-directional parallel interface complying with IEEE 1284. This interface is also
compatible with the conventional Centronics interface. Data transfer from host to printer is performed according to
Centronics standard, called compatible mode. Data transfer from printer to host is performed according to the IEEE
1284 standard, called nibble mode.
In compatible mode, the printer receives data from the computer in handshaking mode based on the Busy and
Acknowledge signals from the printer and the Data Strobe signal from the computer. For the Data Strobe and
Acknowledge signals, the timing of the Busy signal must be as shown in the compatible mode of Figure 5.8a.
To send data from the printer to the host, the interface enters the nibble mode where data is sent in units of four bits
(nibble) using four output signal lines as data paths. The data transfer sequence in nibble mode involves negotiation
phase, reverse idle phase, reverse data transfer phase, and termination phase. Figure 5.8b shows the reverse data
transfer phase where data is sent.