CURDESC_PNTR (CDMA Current Descriptor Pointer – Offset 08h) - 4.1 English

AXI Central Direct Memory Access LogiCORE IP Product Guide (PG034)

Document ID
PG034
Release Date
2022-05-18
Version
4.1 English

This register provides the Current Descriptor Pointer for the AXI CDMA Scatter Gather Descriptor Management.

Figure 2-4:      

X-Ref Target - Figure 2-4

pg034_curdesc_pntr_detail_x13284.jpg

 

Table 2-6:      CURDESC_PNTR Register Details

Bits

Field Name

Default Value

Access Type

CDMA Mode Used

Description

31 to 6

Current Descriptor Pointer

0

R/W

(RO)

SG

Current Descriptor Pointer. Indicates the pointer of the current descriptor being worked on. This register must contain a pointer to a valid descriptor prior to writing to the TAILDESC_PTR register. Failure to do so results in an undefined operation by the CDMA.

When the CDMA SG Engine is running (CDMASR.IDLE = 0), the CURDESC_PNTR register is updated by the SG Engine to reflect the starting address of the current descriptor being executed.

On error detection, the CURDESC_PNTR register is updated to reflect the descriptor associated with the detected error.

The register should only be written by the software application when the AXI CDMA is idle (CDMASR.IDLE = 1). Descriptor addresses written to this field must be aligned to 64-byte boundaries (sixteen 32-bit words). Examples are 0x00, 0x40, 0x80. For 64byte alignment bits [5:0] should be 0. Any other alignment has undefined results.

This register is cleared when CDMACR.SGMode = 0.

5 to 0

Reserved

0

RO

N/A

Writing to these bits has no effect and they are always read as zeros.

Notes:

1.RO = Read Only. Writing has no effect.

2.R/W = Read/Write