SuperH (SH) 64-Bit RISC Series SH-5 System Architecture, Volume ...

PRELIMINARY DATADMAC SuperHyway transactions 914.5 DMAC SuperHyway transactionsThis section describes the different types of transactions that involve the DMACmodule. In particular the treatment of requests received and the types of requeststhat are generated in response to its programming.4.5.1 DMAC as a request targetThe DMAC supports only quadword (that is, 64-bit) load and store requests to theregisters listed in Table 17 on page 64. All other accesses will generate an errorresponse and set the appropriate bit in the VCR register.• If the request is of any other type than a load8 or store8 the BAD_OPC field ofthe DMAC.VCR will be set and an error response will be sent to the initiator. A listof the operations available on the SuperHyway are given in Table 2 on page 17• If the request is to an address mapped to this module but not listed in Table 17on page 64 then the BAD_ADDR field of the DMAC.VCR will be set and an errorresponse will be sent to the initiator. The range of addresses allocated to thismodule is specified in the system address map given in Table 4 on page 26.4.5.2 DMAC as a request initiatorThe DMAC initiates requests only as a result of enabled DMA channels. Table 29 onpage 91 shows the correspondence between the transfer size field (which is log 2 ofthe transfer size in bytes) and the SuperHyway transaction used to implement thetransfer. The largest transaction type able to be used for a transfer is usedexclusively, so for example, a DMA transfer configured with a TRANSFER.SIZE fieldof 4 will be performed only using load16 and store16 transactions on theSuperHyway.DMAC.CTRL.TRANSFER_SIZESHWY transaction usedD R A FT0 Load8/Store8(with 1 bit set in the mask)1 Load8/Store8(with 2 bits set in the mask)2 Load8/Store8(with 4 bits set in the mask)Table 29: DMAC SHWY transactions05-SA-10001 v1.0SuperH, Inc.SH-5 System Architecture, Volume 1: System