13.5.7 Operational Sequence

A complete descriptor-based operation sequence can be summarized below. This includes both Source Descriptor Table (SDT) and Destination Descriptor Table (DDT) operations with write back enabled.

Table 13-15. Descriptor-Based Operational Sequence
FunctionDetails(1)
Fetch
Read descriptor from location SADDR[23:0] (SDP) if SDTEN = 1.Put SADDRn[15:0] (SPP) into SADDR[15:0] register.
Read descriptor from location DADDR[23:0] (DDP) if DDTEN = 1.Put DADDRn[15:0] (DPP) into DADDR[15:0] register.
Payload Transfer
Read payload from location SADDR[23:0] (SPP) per SIZEn[1:0].If SDTEN = 0, apply SAMODE[1:0] else if SDTEN = 1, restore SADDR[23:0] to original SDP.
Write payload from location DADDR[23:0] (DPP) per SIZEn[1:0].If DDTEN = 0, apply DAMODE[1:0] else if DDTEN = 1, restore DADDR[23:0] to original DDP.
Descriptor Write-Back(2)
Write back SADDRm[15:0] (SPP) subject to SAMODE[1:0] if SDTEN = 1.
  • Apply SAMODE[1:0] to SADDRn[15:0] (SPP).
  • Store updated value to location SADDR[23:0].
Write back DADDRm[15:0] (DPP) subject to SAMODE[1:0] if DDTEN = 1.
  • Apply SAMODE[1:0] to SADDRn[15:0] (SPP).
  • Store updated value to location SADDR[23:0].
Next DP Calculation
SADDR[23:0] = SADDR[23:0] + DPOxM1[6:0] if MATCH = 1 else SADDR[23:0] + DPOxM0[6:0] is MATCH = 0.Only if SDTEN = 1.
DADDR[23:0] = DADDR[23:0] + DPOxM1[6:0] if MATCH = 1 else DADDR[23:0] + DPOxM0[6:0] is MATCH = 0.Only if DDTEN = 1.
Note:
  1. Descriptor fetch is a 32-bit word read operation
  2. Write back is a 16-bit word write operation