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CHIP-SELECT UNIT

14.4 REGISTER DEFINITIONS

Table 14-1 and Table 14-2 list the signals and registers associated with the chip-select unit. There

are seven general-purpose chip-select channels (CSn) and one upper chip-select channel (UCS).

Upon reset, the UCS is enabled with the entire 64 Mbyte memory address space as its address

block. The UCS can be used to select a memory device at the top of the memory address space

so that the processor can fetch the first instruction from address 3FFFFF0H after reset.

Table 14-1. CSU Signals

Device Pin or Internal

Chip-select Signals:

Indicates that the memory or I/O address that the

processor is accessing is in channel

’s active address

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Intel 386 Manual do Utilizador Página 448