Please note: I
use the conventional trailing h to indicate a hexadecimal number.
Pin assignments:
|
Signal name
|
Register bit
|
D-SUB
|
Centronics
|
|
Pin
|
GND
|
Pin
|
GND
|
| Data bit 0 |
D0
|
2
|
19
|
2
|
20
|
| Data bit 1 |
D1
|
3
|
19
|
3
|
21
|
| Data bit 2
|
D2
|
4
|
20
|
4
|
22
|
| Data bit 3 |
D3
|
5
|
20
|
5
|
23
|
| Data bit 4 |
D4
|
6
|
21
|
6
|
24
|
| Data bit 5 |
D5
|
7
|
21
|
7
|
25
|
| Data bit 6 |
D6
|
8
|
22
|
8
|
26
|
| Data bit 7 |
D7
|
9
|
22
|
9
|
27
|
| nError (nFault) |
S3
|
15
|
23
|
32
|
29
|
| Select |
S4
|
13
|
24
|
13
|
28
|
| PaperEnd |
S5
|
12
|
24
|
12
|
28
|
| nAck |
S6
|
10
|
24
|
10
|
28
|
| Busy |
S7
|
11
|
23
|
11
|
29
|
| nStrobe |
C0
|
1
|
18
|
1
|
19
|
| nAutoLF |
C1
|
14
|
25
|
14
|
30
|
| nInit |
C2
|
16
|
25
|
31
|
30
|
| nSelectIn |
C3
|
17
|
25
|
36
|
30
|
| Ground |
GND
|
18-25
|
|
19-30
|
|
Port address:
The most parallel ports are located
at a base address of 378h, 278h, or 3BCh. To find the base address of
a parallel port in Windows 95, open the "Control panel", then
click on "System", "Device manager", "Ports",
select an LPT port, then click the "Resources" tab. The addresses
of installed parallel ports are also displayed in the CMOS setup screens
that you can access when you boot your computer.
Visual Basic:
In Visual BASIC you have to use a DLL to
access the ports. Jan Axelson programmed
two DLLs which allow you to use the QBASIC
INP and OUT instructions. You can download
the DLLs at http://www.lvr.com.
Inpout16.dll is for use with 16-bit programs, and Inpout32.dll is for
use with 32-bit programs. Although the program code to call the Inp
and Out routines is identical for both types, each requires a different
DLL and declarations.
Instructions to read and write to the port:
read instruction: xx=INP(address)
write insruction: OUT(address),xx
You can write to the data port (D0-D7) at the base address. D0 is the least
significant bit and D7 is the most significant
bit. For example "OUT(889),85"
writes 01010101(=85 decimal)to the port address
378h (= 889 decimal).
You can read the status port (S3-S7) at the base address+1. At Bit 7(S7)
you will read the inverted signal of the
connector. S0 - S2 are usually not in use
and read as low signals. When all signals
are high you will read 78h (01111000 = 120decimal
= 78h).
You can write to the control port (C0-C3) at base address+2. The bits 0,1
and 3 are inverted so if you write 04h (00000100),
all four bits will be going high and when
you write 0Bh (00001011) all four bits will
be going low.
Do you want to learn more about the parallel
port?
Then take a look at Jan Axelson´s book:
Parallel
Port Complete. -Highly recommended!
| • Copyright 1999 - 2007 by Batronix Elektronik
• |
|
