![](http://datasheet.mmic.net.cn/110000/GT-96100A_datasheet_3491740/GT-96100A_63.png)
GT-96100A Advanced Communication Controller
Revision 1.0
63
3.2
Disabling Address Decoders
CPU interface address decoders can be disabled by setting the Low decoder value higher than the High decoder
value.
Device sub-decoder can be disabled by setting the Low decoder value higher than the High decoder value.
PCI address decoders can be disabled by setting the BAR’s corresponding bit in Base Address registers’ Enable
to 1.
3.3
DMA Unit Address Decoding
The IDMA controller uses the address mapping of the CPU interface.
NOTE: CPU interface address mapping to determine whether the source address is located in one of the
SDRAM banks, Device banks, PCI_0 or PCI_1. The same is true for destination address and next
record address.DMA address decoding is only up to address bit [31]. Bits [35:32] of CPU address
decoding registers are ignored.
3.4
Address Space Decoding Errors
When the CPU tries to access an address from the SysAD that is not supported, the GT-96100A:
Latches the address into the Bus Error Address registers (offsets 0x70,0x78).
Issues a bus error (over SysCmd[5]), if the access was a read access.
Issues an interrupt, if the access was a read or write access.
This feature is useful during software debugging, when errant code can cause fetches from unsupported
addresses.
When SysAD matches one of CPU interface address spaces, but misses the associated subdecoders, the GT-
96100A:
Issues a bus error (over SysCmd[5]), if the access was a read access.
Sets the MemOut bit in the Interrupt Cause register.
When a PCI access hits in a Base Address register then misses in the associated subdecoders:
Random data is returned on a read and write data is discarded.
Latches the address into the Address Decode Error register (offset 0x470).
The MemOut bit in the Interrupt Cause register is also set.
Accesses that miss all of the GT-96100A BARs result in no response at all from the GT-96100A.
When a DMA accesses an unmapped address, DMAOut bit in the interrupt Cause register is set.
NOTE: Never program address space decoders to overlap. Programming address space decoders to overlap
results in unpredictable behavior.