NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 303 -
Revision V1.30
NUC97
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T
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CHNIC
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Ordering function in Descriptor fetch mode
5.9.5.7
This function determines the source of next descriptor address. If [ORDEN] is set, the GDMA
controller fetches the next descriptor from current GDMA_DADRx[Descriptor Address] + 16 bytes.
If this bit is cleared, GDMA fetches the next descriptor from the current GDMA_DADRx[Descriptor
Address] .
GDMA_DADRx[ORDEN]
is
only
relevant
to
descriptor-fetch
function
(GDMA_DADRx[NON_DSPTRMODE] = 0).
Channel Reset
5.9.5.8
The Channel reset is turned on when the bit-0 of GDMA_DADRx is set. This function will clear all
status and stop the descriptor based function relative to individual channel. The GDMA_DADRx
register value is 0x05h when reset bit is set.
Non-Descriptor Fetch Function
5.9.5.9
The non-descriptor-fetch function will take place when current GDMA_DADRx[NON_DSPTRMODE] is
set and the GDMA_DADRx register will have no any intention for the GDMA controller.
The default value of GDMA_DADRx is 0x04. Software can clear GDMA_DADRx with value 0x04 as
well. In this mode, software should write a valid source address to the GDMA_SRCBx register, a
destination address to the GDMA_DSTBx register, and a transfer count to the GDMA_TCNTx register.
Next, the GDMA_CTLx of [gdmaen] and [softreq] bits must be set. A non-descriptor fetch is performed
when bus granted. After transferring a number of bytes or words correspond with burst mode or not,
the channel either waits for the next request or continues with the data transfer until the
GDMA_CTCNTx reaches zero. When GDMA_CTCNTx reaches zero, the channel stops operation.
When an error occurs during the GDMA operation, the channel stops unless software clears the error
condition and sets the GDMA_CTLx of [gdmaen] and [softreq] bits field to start again.