Block Transfer Mode - Renesas H8S Series Hardware Manual

7.5.7

Block Transfer Mode

In block transfer mode, transfer is performed with channels A and B used in combination. Block transfer mode can be
specified by setting the FAE bit in DMABCR and the BLKE bit in DMACRA to 1.
In block transfer mode, a transfer of the specified block size is carried out in response to a single transfer request, and this
is executed the specified number of times. The transfer source is specified by MARA, and the transfer destination by
MARB. Either the transfer source or the transfer destination can be selected as a block area (an area composed of a
number of bytes or words).
Table 7-11 summarizes register functions in block transfer mode.
Table 7-11 Register Functions in Block Transfer Mode
Register
23
23
15
Legend:
MARA: Memory address register A
MARB: Memory address register B
ETCRA: Transfer count register A
ETCRB: Transfer count register B
MARA and MARB specify the start addresses of the transfer source and transfer destination, respectively, as 24 bits.
MAR can be incremented or decremented by 1 or 2 each time a byte or word is transferred, or can be fixed.
Incrementing, decrementing, or holding a fixed value can be set separately for MARA and MARB.
Whether a block is to be designated for MARA or for MARB is specified by the BLKDIR bit in DMACRA.
To specify the number of transfers, if M is the size of one block (where M = 1 to 256) and N transfers are to be performed
(where N = 1 to 65,536), M is set in both ETCRAH and ETCRAL, and N in ETCRB.
Figure 7-13 illustrates operation in block transfer mode when MARB is designated as a block area.
Rev.6.00 Oct.28.2004 page 210 of 1016
REJ09B0138-0600H
Function
0 Source address
register
MARA
0 Destination
address register
MARB
7 0 Holds block
size
ETCRAH
Block size
counter
7 0
ETCRAL
0
Block transfer
counter
ETCRB
Initial Setting Operation
Start address of Incremented/decremented
transfer source every transfer, or fixed
Start address of Incremented/decremented
transfer destination every transfer, or fixed
Block size Fixed
Block size Decremented every
transfer; ETCRH value
copied when count reaches
H'00
Number of block Decremented every block
transfers transfer; transfer ends
when count reaches
H'0000