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31
0
7
23
15
Status [30:0]
Byte Count Buffer 1 [12:0]
Byte Count Buffer2
[28:16]
RDES0
RDES1
RDES2
RDES3
Buffer1 Address [31:0]
Buffer2 Address [31:0]/Next Descriptor Address [31:0]
OWN
Receive Timestamp High [31:0]
Receive Timestamp Low [31:0]
Reserved
Extended Status [31:0]
CTRL
CTRL
[15:14]
RDES4
RDES5
RDES6
RDES7
Reserved
Reserved
[30:29]
Functional Description
896
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
Figure 15-6. Enhanced Receive Descriptor Structure
The following tables define the Enhanced Receive Descriptors. RDES0 contains the received frame
status, the frame length, and the descriptor ownership information (see
). RDES1 contains the
buffer sizes and other bits that control the descriptor chain or ring (see
). RDES2 and RDES3
contains the address pointers to the first and second data buffers in the descriptor (see
and
). The availability of the extended status is indicated by Bit 0 of RDES0. RDES6 and RDES7
are available only when the Advanced Timestamp or IP Checksum Full Offload feature is enabled (see
and
Table 15-8. Enhanced Receive Descriptor 0 (RDES0)
Bit
Description
31
OWN: Own Bit
When set, this bit indicates that the descriptor is owned by the DMA. When this bit is reset, it indicates that the
descriptor is owned by the Host. The DMA clears this bit either when it completes the frame reception or when the
buffers that are associated with this descriptor are full.
30
AFM: Destination Address Filter Fail
When set, this bit indicates a frame failed in the DA filter in the MAC.
29:16
FL: Frame Length
These bits indicate the byte length of the received frame that was transferred to the system memory. This field is valid
when the Last Descriptor (RDES0[8]) is set and either the Descriptor Error (RDES0[14]) or the Overflow Error bit
(RDES0[11]) is clear.
When the Last Descriptor bit is not set, this field indicates the accumulated number of bytes that have been transferred
for the current frame. The inclusion of CRC length in the frame length depends on the settings of CRC configuration
bits, ACS and CST in the EMACCFG register.