CHAPTER 6 BUS CONTROL
User’s Manual U14272EJ3V0UM
137
6.6 ISA Bridge
The V
R
4181 has an external bus used for ROM, flash memory, DRAM, and I/O. This bus’s operation emulates an
ISA bus at accesses to external memory and I/O spaces. The V
R
4181 also uses an ISA bus internally for the slow,
embedded peripherals.
Among the pins used for accesses in the external ISA bus, UBE#, IOCS16#, IORDY, IOWR#, and IORD# share
the pins with GPIO(20:16), as well as MEMCS16# with LOCLK. To use these pins as an external ISA bus interface,
make settings in the GIU in advance.
6.7 ISA Bridge Register Set
The following registers provide configuration and control of the ISA Bridge.
Table 6-4. ISA Bridge Registers
Physical address
R/W
Register symbol
Function
0x0B00 02C0
R/W
ISABRGCTL
ISA Bridge control register
0x0B00 02C2
R/W
ISABRGSTS
ISA Bridge status register
0x0B00 02C4
R/W
XISACTL
External ISA control register
Содержание VR4181 mPD30181
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