SPRUGZ8D Datasheet, PDF (1300/3016 Pages) Texas Instruments – Technical Reference Manual

EDMA3 Architecture
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8.4.3.5 Dummy Versus Null Transfer Comparison
There are some differences in the way the EDMA3CC logic treats a dummy versus a null transfer request.
A null transfer request is an error condition, but a dummy transfer is a legal transfer of 0 bytes. A null
transfer causes an error bit (En) in EMR to get set and the En bit in SER remains set, essentially
preventing any further transfers on that channel without clearing the associated error registers.
Table 8-4 summarizes the conditions and effects of null and dummy transfer requests.
Table 8-4. Dummy and Null Transfer Request
Feature
EMR/EMRH/QEMR is set
SER/SERH/QSER remains set
Link update (STATIC = 0 in OPT)
QER is set
IPR/IPRH CER/CERH is set using early completion
Null TR
Yes
Yes
Yes
Yes
Yes
Dummy TR
No
No
Yes
Yes
Yes
8.4.3.6 Parameter Set Updates
When a TR is submitted for a given DMA/QDMA channel and its corresponding PaRAM set, the
EDMA3CC is responsible for updating the PaRAM set in anticipation of the next trigger event. For events
that are not final, this includes address and count updates; for final events, this includes the link update.
The specific PaRAM set entries that are updated depend on the channel’s synchronization type (A-
synchronized or B-synchronized) and the current state of the PaRAM set. A B-update refers to the
decrementing of BCNT in the case of A-synchronized transfers after the submission of successive TRs. A
C-update refers to the decrementing of CCNT in the case of A-synchronized transfers after BCNT TRs for
ACNT byte transfers have submitted. For AB-synchronized transfers, a C-update refers to the
decrementing of CCNT after submission of every transfer request.
See Table 8-5 for details and conditions on the parameter updates. A link update occurs when the PaRAM
set is exhausted, as described in Section 8.4.3.7.
After the TR is read from the PaRAM (and is in process of being submitted to EDMA3TC), the following
fields are updated if needed:
• A-synchronized: BCNT, CCNT, SRC, DST.
• AB-synchronized: CCNT, SRC, DST.
The following fields are not updated (except for during linking, where all fields are overwritten by the link
PaRAM set):
• A-synchronized: ACNT, BCNTRLD, SRCBIDX, DSTBIDX, SRCCIDX, DSTCIDX, OPT, LINK.
• AB-synchronized: ACNT, BCNT, BCNTRLD, SRCBIDX, DSTBIDX, SRCCIDX, DSTCIDX, OPT, LINK.
1300
Enhanced Direct Memory Access Controller
SPRUGZ8D – 14 November 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated
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