Intel® Agilex™ Hard Processor System Technical Reference Manual

ID 683567
Date 2/14/2023
Public

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17.6.3.2.2. Receive Descriptor Field 1 (RDES1)

Table 177.  Receive Descriptor Field 1 (RDES1)

Bit

Description

31

DIC: Disable Interrupt on Completion

When set, this bit prevents setting the Status Register’s RI bit (CSR5[6]) for the received frame ending in the buffer indicated by this descriptor. As a result, the RI interrupt for the frame is disabled and is not asserted to the Host.

30:29

Reserved 

28:16

RBS2: Receive Buffer 2 Size

These bits indicate the second data buffer size, in bytes. The buffer size must be a multiple of 4, even if the value of RDES3 (buffer2 address pointer) in the Receive Descriptor Field 3 (RDES3) is not aligned to the bus width. If the buffer size is not an appropriate multiple of 4, the resulting behavior is undefined. This field is not valid if RDES1[14] is set. For more information about calculating buffer sizes, refer to the Buffer Size Calculations section in this chapter.

15

RER: Receive End of Ring

When set, this bit indicates that the descriptor list reached its final descriptor. The DMA returns to the base address of the list, creating a descriptor ring. 

14

RCH: Second Address Chained

When set, this bit indicates that the second address in the descriptor is the next descriptor address rather than the second buffer address. When this bit is set, RBS2 (RDES1[28:16]) is a “don’t care” value. RDES1[15] takes precedence over RDES1[14]. 

13

Reserved 

12:0

RBS1: Receive Buffer 1 Size

Indicates the first data buffer size in bytes. The buffer size must be a multiple of 4, even if the value of RDES2 (buffer1 address pointer), in the Receive Descriptor Field 2 (RDES2), is not aligned. When the buffer size is not a multiple of 4, the resulting behavior is undefined. If this field is 0, the DMA ignores this buffer and uses Buffer 2 or the next descriptor depending on the value of RCH (Bit 14). For more information about calculating buffer sizes, refer to the Buffer Size Calculations section in this chapter.