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IBM2520L8767
IBM Processor for ATM Resources
General Purpose DMA (GPDMA)
Page 138 of 553
atmrm.chapt04.01
08/27/99
4.7: GPDMA DMA Max Burst Time
Used to limit the number of cycles a master can burst on the PCI bus. When a DMA burst is started a counter
is loaded with the value in this register. When the counter expires and the current access completes, the PCI
bus will be released for use by another bus master. Writing a non zero value to this register enables this func-
tion
24
Reserved.
Was Queue on DMA Complete. Now handled by DMAQS. When this bit is set, the upper
26 bits of the GPDMA System Descriptor Address register will be queued to the DMA
event queue when the DMA completes. If descriptors are not being used to set up the
DMA, the GPDMA System Descriptor Address register should be loaded, before starting
the DMA, with a value to identify this transfer. If descriptors are being used, the GPDMA
System Descriptor Address register will be loaded automatically with the system address
of the descriptor block at the time it is processed.
23
Reserved.
Was Inhibit Status Update when DMA Complete. Normally a bit will be set in the status
register when the DMA completes without error. If this bit is set, this update will not be
done. This bit is useful when multiple DMAs are to be done and an interrupt is only
desired on the last transfer. The DMA error status bits are unaffected by this bit.
22
Reserved.
Was Auto Increment Destination Address. This bit is only used when enqueuing descrip-
tors. If this bit is set the destination address will be sourced from the previous DMA
instead of the destination address specified in the descriptor.
21
Register/Memory
Destination Address.
If this bit is set, the destination address is a register address. If this bit is not set, the des-
tination address is a memory address. If the destination address is a system address this
bit should cleared. I/O DMA cycles on the PCI bus are not implemented.
20
System/IBM2520L8767
Destination Address.
If this bit is set, the destination address is a PCI bus address. If this bit is not set, the des-
tination address is internal to the chip.
19
Data/Address Source
Address.
If this bit is set, the Source Address Register contains the source data. If this bit is not
set, the Source Address Register contains the source address.
18
Reserved.
Was Auto Increment Source Address. This bit is only used when enqueuing descriptors.
If this bit is set, the source address will be sourced from the previous DMA instead of the
source address specified in the descriptor.
17
Register/Memory
Source Address.
If this bit is set, the source address is a register address. If this bit is not set, the source
address is a memory address. If the source address is a system address, this bit should
cleared. I/O DMA cycles on the PCI bus are not implemented.
16
System/IBM2520L8767
Source Address.
If this bit is set, the source address is a PCI bus address. If this bit is not set, the source
address is internal to the chip.
15-0
Byte Transfer Count.
These bits indicate the number of bytes to transfer. A non-zero value in this field will start
the DMA transfer.
Length
24 bits
Type
Read/Write
Address
XXXX 0158
Power on Value
X’000’
Restrictions
None
Bit(s)
Function
Description