Read and Write Priorities

Zynq UltraScale+ Device Technical Reference Manual (UG1085)

Document ID
UG1085
Release Date
2022-09-15
Revision
2.3 English

The read channel of a port can be set to operate as high priority reads (HPR), low priority reads (LPR), or video/isochronous priority reads (VPR). The write channel of a port can be set as best-effort writes (BEW) or video/isochronous priority writes (VPW). The PA gives higher priority to an HPR read port than an LPR/VPR read port. VPRs that are not expired are treated as LPRs from the arbiter point of view. If a VPR transaction expires in the XPI, it has higher priority than HPRs or writes.

BEW and VPW have the same initial priority. VPWs that are not expired, are treated as BEWs from the arbiter point of view. If a VPW transaction expires in the XPI, it has higher priority than BEWs. When multiple VPR/VPW commands expire simultaneously, the PA executes them in round-robin order to the DDRC.