IBM PC 100, Technical Manual

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Chapter 1. System Description
IRQ and DMA Channel Assignments
The following figures list the interrupt request (IRQ) and direct memory access (DMA) channel
assignments.
Interrupt Request Assignments (IRQ)
DMA Channel Assignments
Figure 5 (Page 2 of 2). DMA I/O Addresses for Memory Addresses, Word Counts, and Command/Status
Registers
Address (hex) Description Bits Byte Pointer
00DF Channels 5–7, 8- or 16-bit mode select 00–07
ñ
Upper byte of Memory Address register
Figure 6. Interrupt Request Assignments
Interrupt
Request (IRQ)
System Resource
NMI Critical system error
SMI System/power management interrupt
0 Reserved (internal timer)
1 Reserved (keyboard buffer full)
2 Reserved (cascade interrupt from slave)
3 Serial port 2
ñ
4 Serial port 1
ò
5 Parallel port 2
ñ
6 Diskette controller
ò
7 Parallel port 1
ò
8 Reserved (real-time clock)
9 Video adapter (if installed)
ñ
10 ISA/PCI bus
11 ISA/PCI bus
12 Mouse port
ñ
13 Reserved (math coprocessor)
14 IDE Channel 1
ñ
15 IDE Channel 2
ò
ñ
If not assigned, this resource is available for the ISA/PCI bus.
ò
If not assigned, this resource is available for the ISA bus.
Figure 7. DMA Channel Assignments
DMA
Channel Data Width
System Resource
0 8 bits ISA bus
ñ
1 8 bits ISA bus
ñ
2 8 bits Reserved (diskette drive)
3 8 bits ECP/EPP parallel port
ñ
4 Reserved (cascade channel)
5 16 bits ISA bus
6 16 bits ISA bus
7 16 bits ISA bus
ñ
If not assigned, this resource is available for the ISA bus.
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