QUOTE

8 data lines - Write only

Register DB25 LM018L
Bit Pin No Pin No Function
D0 => 2

---

7 => DB0
D1 => 3

---

8 => DB1
D2 => 4

---

9 => DB2
D3 => 5

---

10 => DB3
D4 => 6

---

11 => DB4
D5 => 7

---

12 => DB5
D6 => 8

---

13 => DB6
D7 => 9

---

14 => DB7
C2 => 16

---

6 => E Enable: H,H->L
~C3 => 17

---

4 => RS Register Select
L: Instr, H: Data
+- 5 => R/W Read/Write
| H: <=, L: =>
Ground 18-25

---

+- 1 => Vss 0V
2 => Vdd +5V @ 3.0mA max
3 => Vo -

IBM-PC Parallel Port Registers (x unused, - unavailable)

7 6 5 4 3 2 1 0 I/O Port
+---+---+---+---+---+---+---+---+
DATA |DB7|DB6|DB5|DB4|DB3|DB2|DB1|DB0| Base = 278/378/3BC Hex
+---+---+---+---+---+---+---+---+
STATUS | x | x | x | x | x | - | - | - | Base + 1
+---+---+---+---+---+---+---+---+
CONTROL | - | - | - | - |RS | E | x | x | Base + 2
+---+---+---+---+---+---+---+---+

N.B. C0, C1 & C3 are inverted - i.e. C0 = 1 will cause Parallel Port pin 1 to go LOW.

If timing is non-critical (no need to check Busy Flag DB7) then the R/W line - Pin 5 - can be tied to Ground (LOW).

C0 and C1 can be used as select-lines for up to 4 LCD Panels.

You can use the Game Port as a source for 5v

The pin-outs of the IBM-PC GamePort - use any +5v & GND pins

1 XY1 (+5v) 9 XY2 (+5v)
2 Switch 1 10 Switch 4
3 X1 11 X2
4 Switch 1 (GND) 12 Switch 3&4 (GND)
5 Switch 2 (GND) 13 Y2
6 Y1 14 Switch 3
7 Switch 2 15 N.C.
8 N.C.

QUOTE

The following sample program in C, shows
how you can obtain the addresses of your printer ports.
#include <stdio.h>
#include <dos.h>
void main(void)
{
unsigned int far *ptraddr; /* Pointer to location of Port Addresses */
unsigned int address; /* Address of Port */
int a;
ptraddr=(unsigned int far *)0x00000408;
for (a = 0; a < 3; a++)
{
address = *ptraddr;
if (address == 0)
printf("No port found for LPT%d \n",a+1);
else
printf("Address assigned to LPT%d is %Xh\n",a+1,address);
*ptraddr++;
}
}