AB-2061G-33 Datasheet, PDF (11/32 Pages) List of Unclassifed Manufacturers – 33Mhz PCI to Local Bus Interface

Accessing On Chip Registers
Most registers in the device are not directly accessible; an indirect scheme is
used whereby the internal address of the register required is written to a
REGISTER_ADDRESS register and data transferred to and from the register via
the REGISTER_DATAn port. Some registers are directly accessible for reasons of
speed.
The chip appears to the local processor to be a set of 16 8-bit ports starting at
some system-defined base address. These are:
Address Name
Base Offset
Function
0
REGISTER_ADDRESS
Indirect address register, holds
the address of the register to be
accessed through
REGISTER_DATA0..3
1
RESOURCE_STATUS (R) Read : Returns status of DMA and
FIFOs
RESOURCE_CONTROL (W) Write : DMA/PCI control bits
2
FIFO_DATA0
Read : Data from PCI through FIFO1
3
FIFO_DATA1 (16 bit only) Write : Data to PCI through FIFO2
4
REGISTER_DATA0
5
REGISTER_DATA1
6
REGISTER_DATA2
7
REGISTER_DATA3
Byte 0 of indirectly accessed
register
Byte 1 of indirectly accessed
register
Byte 2 of indirectly accessed
register
Byte 3 of indirectly accessed
register
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