![Texas Instruments SimpleLink Ethernet MSP432E401Y Technical Reference Manual Download Page 903](http://html1.mh-extra.com/html/texas-instruments/simplelink-ethernet-msp432e401y/simplelink-ethernet-msp432e401y_technical-reference-manual_1095578903.webp)
Functional Description
903
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
In Operate on Second Frame (OSF) mode, the RUN state TX DMA operates in the following sequence:
1. The DMA operates as described in Step 1 to Step 6 of
2. Without closing the previous frame's last descriptor, the DMA fetches the next descriptor.
3. If the DMA owns the acquired descriptor, the DMA decodes the transmit buffer address in this
descriptor. If the DMA does not own the descriptor, the DMA goes into SUSPEND mode and skips to
Step 7.
4. The DMA fetches the Transmit frame from system memory and transfers the frame until the end-of-
frame data is reached. It closes the intermediate descriptors if this frame is split across multiple
descriptors.
5. The DMA waits for the previous frame's transmission status and timestamp. When the status is
available, the DMA writes the timestamp to TDES6 and TDES7, if such timestamp was captured (as
indicated by a status bit). The DMA then writes the status, with a cleared OWN bit, to the
corresponding TDES0, thus closing the descriptor. If timestamping was not enabled for the previous
frame, the DMA does not alter the contents of TDES6 and TDES7.
6. If enabled, the Transmit interrupt (TI) bit is set in the EMACDMARIS register, the DMA fetches the next
descriptor and then proceeds to Step 3 (when Status is normal). If the previous transmission status
shows an underflow error, the DMA goes into SUSPEND mode
7. In SUSPEND mode, if a pending status and timestamp are received, the DMA writes the timestamp (if
enabled for the current frame) to TDES6 and TDES7, then writes the status to the corresponding
TDES0. It then sets relevant interrupts and returns to SUSPEND mode.
8. The DMA can exit SUSPEND mode and enter the RUN state only after receiving the Transmit Poll
demand in the EMACTXPOLLD register.
NOTE:
The DMA fetches the next descriptor in advance before closing the current descriptor.
Therefore, the descriptor chain should have more than two different descriptors for correct
and proper operation.
shows the flow for the TX DMA Operate-On-Second-Frame (OSF) operation.