Physics 413 Chapter 10

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Physics 413Chapter 10
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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

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Parallel Port (DB-25 connector)
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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.

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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

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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 gt 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

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Memory Map

• 00000-003FF 1K Interrupt Vectors
• A0000 - BFFFF 128 K Video RAM
• B8000-BBFFF 16K CGA
• A0000-AFFFF 64K VGA
• 00400-004FF 1/4 K BIOS Data Area
• F0000 - FFFFF 64 K BIOS ROM

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I / O Map

• 00 - 1F DMA controller 8237A
• 20 - 21 PIC1 (master) 8259A
• 60 - 63 Keyboard controller 8042
• 70 - 71 Real-time clock MC 146818
• 80 - 83 DMA page register 74LS612
• 1F0-1F8 Hard-disk controller
• 200-207 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)