NXP Semiconductors K32 L2A Series, Reference Manual, Page: 479 / 1379

If e_sg = 0b and the dlast_sga changed, the dynamic link attempt was successful (the
new TCD’s e_sg value cleared the e_sg bit).
20.5.8 Suspend/resume a DMA channel with active hardware
service requests
The DMA allows the user to move data from memory or peripheral registers to another
location in memory or peripheral registers without CPU interaction. Once the DMA and
peripherals have been configured and are active, it is rare to suspend a peripheral’s
service request dynamically. In this scenario, there are certain restrictions to disabling a
DMA hardware service request. For coherency, a specific procedure must be followed.
This section provides guidance on how to coherently suspend and resume a Direct
Memory Access (DMA) channel when the DMA is triggered by a slave module such as
the Serial Peripheral Interface (), ADC, or other module.
20.5.8.1 Suspend an active DMA channel
To suspend an active DMA channel:
1. Stop the DMA service request at the peripheral first. Confirm it has been disabled by
reading back the appropriate register in the peripheral.
2. Check Hardware Request Status Register (DMA_HRS) to ensure there is no service
request to the DMA channel being suspended. Then disable the hardware service
request by clearing the ERQ bit on the appropriate DMA channel.
20.5.8.2 Resume a DMA channel
To resume a DMA channel:
1. Enable the DMA service request on the appropriate channel by setting its ERQ bit.
2. Enable the DMA service request at the peripheral.
For example, assume a module is set as a master for transmitting data via a DMA service
request when the has an empty slot. The DMA will transfer the next command and data
to the TXFIFO upon the request. If the user needs to suspend the DMA/ transfer loop,
perform the following steps:
1. Disable the DMA service request at the source by writing 0 to . Confirm that is 0.
Chapter 20 Enhanced Direct Memory Access (eDMA)
K32 L2A Reference Manual, Rev. 2, 01/2020
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