Datasheet

Section 7 DMA Controller (DMAC)
R01UH0310EJ0500 Rev. 5.00 Page 357 of 1384
Sep 25, 2012
H8S/2426, H8S/2426R, H8S/2424 Group
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)
DTID
· 2
DTSZ
· ETCRH
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
not sent to the CPU or DTC. By setting the DTE bit to 1 again after it has been cleared, the
operation can be restarted from the transfer after that terminated when the DTE bit was cleared.