Datasheet
Section 8 DMA Controller (DMAC)
Rev. 6.00 Mar. 18, 2010 Page 241 of 982
REJ09B0054-0600
8.5.4 Repeat Mode
Repeat mode can be specified by setting the RPE bit in DMACR to 1, and clearing the DTIE bit in
DMABCRL to 0. In repeat mode, MAR is updated after each byte or word transfer in response to
a single transfer request, and this is executed the number of times specified in ETCRL. On
completion of the specified number of transfers, MAR and ETCRL are automatically restored to
their original settings and operation continues. One address is specified by MAR, and the other by
IOAR. The transfer direction can be specified by the DTDIR bit in DMACR. Table 8.7
summarizes register functions in repeat mode.
Table 8.7 Register Functions in Repeat Mode
Function
Register DTDIR = 0 DTDIR = 1 Initial Setting Operation
23 0
MAR
Source
address
register
Destination
address
register
Start address of
transfer destination
or transfer source
Incremented/
decremented every
transfer
Initial setting is
restored when value
reaches H'0000
23 0
IOAR
15
H'FF
Destination
address
register
Source
address
register
Start address of
transfer source or
transfer destination
Fixed
0
ETCRH
7
Holds number of
transfers
Number of transfers Fixed
0
ETCRL
7
Transfer counter Number of transfers Decremented every
transfer
Loaded with ETCRH
value when count
reaches H'00
MAR specifies the start address of the transfer source or transfer destination as 24 bits. MAR is
incremented or decremented by 1 or 2 each time a byte or word is transferred. IOAR specifies the
lower 16 bits of the other address. The upper 8 bits of IOAR have a value of H'FF. The number of
transfers is specified as 8 bits by ETCRH and ETCRL. The maximum number of transfers, when
H'00 is set in both ETCRH and ETCRL, is 256.
In repeat mode, ETCRL functions as the transfer counter, and ETCRH is used to hold the number
of transfers. ETCRL is decremented by 1 each time a data transfer is executed, and when its value
reaches H'00, it is loaded with the value in ETCRH. At the same time, the value set in MAR is