Hitachi H8S/2378, H8S/2378R Series Hardware Manual page 322

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 7.7
summarizes register functions in repeat mode.
Table 7.7 Register Functions in Repeat Mode
Register
23
MAR
23 15
H'FF
IOAR
7
ETCRH
7
ETCRL
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
restored in accordance with the values of the DTSZ and DTID bits in DMACR. The MAR
restoration operation is as shown below.
MAR = MAR – (–1)
The same value should be set in ETCRH and ETCRL.
In repeat mode, operation continues until the DTE bit in DMABCRL is cleared. To end the
transfer operation, therefore, the DTE bit should be cleared to 0. A transfer end interrupt request is
Rev. 1.0, 09/01, page 278 of 904
Function
DTDIR = 0 DTDIR = 1 Initial Setting
0 Source
address
register
0 Destination
address
register
0 Holds number of
transfers
Transfer counter
0
DTID DTSZ
· 2 · ETCRH
Destination Start address of
address transfer destination
register or transfer source
Source Start address of
address transfer source or
register transfer destination
Number of transfers
Number of transfers
Operation
Incremented/
decremented every
transfer.
Initial setting is
restored when value
reaches H'0000
Fixed
Fixed
Decremented every
transfer.
Loaded with ETCRH
value when count
reaches H'00