SH7670 Datasheet, PDF (562/1292 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7670 Series

Section 14 DMAC That Works with Encryption/Decryption and Forward Error Correction Core (A-DMAC)
14.4.2 Basic Channel Operation
When "1" is written to the C[i]C_E bit of the channel [i] processing control register (C[i]C),
channel [i] reads the descriptor from the C[i]DCA31 to C[i]DCA4 addresses. If a fixed length is
set in C[i]C_VLD, the first 32 bytes are continuously read. If variable length is set, the remaining
16 bytes are read according to the previously explained conditions.
If the C[i]F0 flag of the first longword of a descriptor is 1, the descriptor is fetched to the
appropriate register of channel [i] processing descriptor 0 (C[i]D0) to channel [i] processing
descriptor 4 (C[i]D4). After 1-descriptor processing ends, channel [i] sets the C[i]F0 flag to 0 and
writes back to the original area.
Any number of descriptors can be allocated onto memory in the ring form. Processing is started
from the descriptor allocated to the address indicated by the channel [i] processing descriptor
current address register (C[i]DCA). If descriptors where the C[i]F0 flag of channel [i] processing
descriptor 0 (C[i]D0) is set to 1 continue, channel [i] processes them one after another. If the
C[i]F1 flag of channel [i] processing descriptor 0 (C[i]D0) is 1, channel [i] assumes that the end of
descriptor ring was detected and processes the descriptor allocated to the address indicated by the
channel [i] processing descriptor start address register (C[i]DSA). To end descriptor processing,
allocate the invalid descriptor where the C[i]F0 flag of channel [i] processing descriptor 0
(C[i]D0) is set to 0.
If processing for single continuous data is divided into several descriptors, the data size of each
processing must be saved between several descriptor processing. Conversely, to handle different
data, the data size of each processing must be initialized. For this reason, whether the descriptor
currently being executed handles the end of continuous data must be indicated in the descriptor.
Set this in the C[i]F2 flag.
The A-DMAC does not allow you to set data size 0 in C[i]D315 to C[i]D30.
Rev. 1.00 Nov. 14, 2007 Page 536 of 1262
REJ09B0437-0100