NXP Semiconductors QorIQ LS1012A Reference Manual

Table 32-6. Isochronous transaction descriptor (iTD) (continued)Buffer pointer (page 5) Reserved 0x38Buffer pointer (page 6) Reserved 0x3C1. Host controller read/write; all others read-only.2. These fields may be modified by the host controller if the I/O field indicates an OUT.32.5.3.1 Next link pointer-iTDThe first DWord of an iTD is a pointer to the next schedule data structure, as shown inthe table below.Table 32-7. Next schedule element pointerBits Name Description31-5 Link Pointer Correspond to memory address signals [31:5], respectively. This field points to another isochronoustransaction descriptor (iTD/siTD) or queue head (QH).4-3 - Reserved, should be cleared. These bits are reserved and their value has no effect on operation.Software should initialize this field to zero.2-1 Typ Indicates to the host controller whether the item referenced is an iTD, siTD or a QH. This allows thehost controller to perform the proper type of processing on the item after it is fetched. Value encodingsare:00 iTD (isochronous transfer descriptor)01 QH (queue head)10 siTD (split transaction isochronous transfer descriptor)11 FSTN (frame span traversal node)0 T Terminate1 Link Pointer field is not valid.0 Link Pointer field is valid.32.5.3.2 iTD transaction status and control listDWords 1-8 constitute eight slots of transaction control and status.Each transaction description includes the following:• Status results field• Transaction length (bytes to send for OUT transactions and bytes received for INtransactions).• Buffer offset. The PG and Transaction n Offset fields are used with the buffer pointerlist to construct the starting buffer address for the transaction.Chapter 32 Universal Serial Bus Interface 2.0QorIQ LS1012A Reference Manual, Rev. 1, 01/2018NXP Semiconductors 1973