1. Physics 413 Chapter 10

2. IBM PC Interfacing
The parallel port is a 25-pin DB-25 (D-shaped) connector accessible from the back of the PC
The expansion slot provides access to the address bus, data bus, several IRQ lines, clock signal, and several control lines

3. Parallel Port (DB-25 connector)

4. DB-25 Pin Functions
Pins 2 through 9 are the 8 data pins D0 through D7. Data Port = “base” address of the printer port(378)
Pins 18 through 25 are ground pins
Pins 1, 14, 16, and 17 are -strobe, -auto feed, initialize, and -select input. These are all outputs to the printer and accessed via the Control Port whose address is base + 2
Pins 10, 11, 12, 13, and 15 are -acknowledge, busy, paper empty, select, and -error. These are outputs from the printer and accessed via the Status Port whose address is base + 1.

5. Moving data IN and OUT
IN Reads in the data from a peripheral device (I/O)
OUT Sends data out to a peripheral device(I/O)
MOV sends data to and from memory

6. IN and OUT the right way . . .
IN AL, 40H Data from port 40h is read into AL
OUT 40H, AL Data from AL is sent to port 40h
IN AL, 340H Illegal because 340 is > FF
MOV DX, 378 Data from port 378 is read into AL
IN AL, DX
OUT DX, AL Data from AL sent to port 378

7. Memory Map 00000-003FF 1K Interrupt Vectors
A BFFFF 128 K Video RAM
B8000-BBFFF 16K CGA
A0000-AFFFF 64K VGA
FF 1/4 K BIOS Data Area
F FFFFF 64 K BIOS ROM

8. I / O Map 00 - 1F DMA controller 8237A 20 - 21 PIC1 (master) 8259A
Keyboard controller 8042
Real-time clock MC
DMA page register 74LS612
1F0-1F8 Hard-disk controller
Game adapter
278-27F Parallel "printer" port 2 (LPT2)
300-31F Prototype adapter for interfacing
378-37F Parallel "printer" port1 (LPT1)
3D0-3DF CGA / VGA controller
3F0-3F7 "Floppy" disk controller
3F8-3FF Serial port1 (asynchronous: COM1)