B&B Electronics Parallel Printer Card PIOC Manuale Utente Scaricare il pdf (Pagina 3)

Interfacing the Standard Parallel Port http://www.senet.com.au/~cpeacock

Interfacing the Standard Parallel Port Page 3

has power. 1284 Type C connectors are recommended for new designs, so we can look forward on

seeing these new connectors in the near future.

Pin No (D-

Type 25)

Pin No

(Centronics)

SPP Signal Direction

In/out

Inverted

1 1 nStrobe In/Out Control Yes

2 2 Data 0 Out Data

3 3 Data 1 Out Data

4 4 Data 2 Out Data

5 5 Data 3 Out Data

6 6 Data 4 Out Data

7 7 Data 5 Out Data

8 8 Data 6 Out Data

9 9 Data 7 Out Data

10 10 nAck In Status

11 11 Busy In Status Yes

12 12 Paper-Out

PaperEnd

In Status

13 13 Select In Status

14 14 nAuto-Linefeed In/Out Control Yes

15 32 nError / nFault In Status

16 31 nInitialize In/Out Control

17 36 nSelect-Printer

nSelect-In

In/Out Control Yes

18 - 25 19-30 Ground Gnd

Table 1. Pin Assignments of the D-Type 25 pin Parallel Port Connector.

The above table uses "n" in front of the signal name to denote that the signal is active low. e.g.

nError. If the printer has occurred an error then this line is low. This line normally is high, should the

printer be functioning correctly. The "Hardware Inverted" means the signal is inverted by the Parallel

card's hardware. Such an example is the Busy line. If +5v (Logic 1) was applied to this pin and the

status register read, it would return back a 0 in Bit 7 of the Status Register.

The output of the Parallel Port is normally TTL logic levels. The voltage levels are the easy

part. The current you can sink and source varies from port to port. Most Parallel Ports implemented in

ASIC, can sink and source around 12mA. However these are just some of the figures taken from Data

sheets, Sink/Source 6mA, Source 12mA/Sink 20mA, Sink 16mA/Source 4mA, Sink/Source 12mA.

As you can see they vary quite a bit. The best bet is to use a buffer, so the least current is drawn from

the Parallel Port.

1 2 3 4 5 6 7 8 ... 16 17

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