Renesas H8/3067 Series User Manual page 273

Section 7 DMA Controller
executed. If level sensing is selected, the transfer continues while DREQ is low, until the transfer
is completed. The bus is released temporarily after each byte or word has been transferred,
however. If the DREQ input goes high during a transfer, the transfer is suspended after the current
byte or word has been transferred. When DREQ goes low, the request is held internally until one
byte or word has been transferred. The TEND signal goes low during the last write cycle.
In block transfer mode, an external request operates as follows. Only edge-sensitive transfer
requests are possible in block transfer mode. Each time a high-to-low transition of the DREQ
input is detected, a block of the specified size is transferred. The TEND signal goes low during the
last write cycle in each block.
Activation by Auto-Request: The transfer starts as soon as enabled by register setup, and
continues until completed. Cycle-steal mode or burst mode can be selected.
In cycle-steal mode the DMAC releases the bus temporarily after transferring each byte or word.
Normally, DMAC cycles alternate with CPU cycles.
In burst mode the DMAC keeps the bus until the transfer is completed, unless there is a higher-
priority bus request. If there is a higher-priority bus request, the bus is released after the current
byte or word has been transferred.
Rev. 4.00 Jan 26, 2006 page 249 of 938
REJ09B0276-0400