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6.2 ISA I/O Address Map
Table 25 lists the AlphaPC 164 ISA I/O space address mapping.
Table 25 ISA I/O Address Map
Range (hex)
000-00F
020-021
040-043
060-061
070
080-08F
0A0-0A1
0C0-0DF
2F8-2FF
370-377
3BC-3BF
3F0-3F7
3F8-3FF
800
801
804-806
6.3 Flash ROM Address Map
The address range for the flash ROM is FFF8.0000–FFFF.FFFF. Flash space of
1MB is obtained by double mapping this 512KB space. FLASH_ADR19 register at
I/O location 800h provides this function. Writing a 0 to this location enables the
lower 512KB of flash. Writing a 1 to this location enables the upper 512KB of flash.
22
Interrupts and ISA Bus Addresses
Usage
8237 DMA #1
8259 PIC #1
8253 timer
Ubus IRQ12 and NMI control
CMOS RAM address and NMI mask register
DMA page registers
8259 PIC #2
8237 DMA #2
Serial port—COM2
Secondary diskette
Parallel port—LPT1
Primary diskette
Serial port—COM1
FLASH_ADR19 register
AlphaPC 164 configuration register
PCI interrupt registers
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