Datasheet

Section 7 DMA Controller (DMAC)
Page 368 of 1408 R01UH0309EJ0500 Rev. 5.00
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
7.5.6 Normal Mode
In normal mode, transfer is performed with channels A and B used in combination. Normal mode
can be specified by setting the FAE bit in DMABCRH to 1 and clearing the BLKE bit in
DMACRA to 0. In normal mode, MAR is updated after data transfer of a byte or word in response
to a single transfer request, and this is executed the number of times specified in ETCRA. The
transfer source is specified by MARA, and the transfer destination by MARB. Table 7.9
summarizes register functions in normal mode.
Table 7.9 Register Functions in Normal Mode
Register Function Initial Setting Operation
23 0
MARA
Source address
register
Start address of
transfer source
Incremented/decremented
every transfer, or fixed
23 0
MARB
Destination
address register
Start address of
transfer destination
Incremented/decremented
every transfer, or fixed
15 0
ETCRA
Transfer counter Number of transfers Decremented every
transfer; transfer ends
when count reaches
H'0000
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.
The number of transfers is specified by ETCRA as 16 bits. ETCRA is decremented by 1 each time
a transfer is performed, and when its value reaches H'0000 the DTE bit in DMABCRL is cleared
and transfer ends. If the DTIE bit in DMABCRL is set to 1 at this time, an interrupt request is sent
to the CPU or DTC. The maximum number of transfers, when H'0000 is set in ETCRA, is 65,536.
Figure 7.11 illustrates operation in normal mode.