SH7032 Datasheet, PDF (220/687 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Section 9 Direct Memory Access Controller (DMAC)
9.3.2 DMA Transfer Requests
DMA transfer requests are basically generated in either the data transfer source or destination, but
they can also be generated by devices and on-chip supporting modules that are neither the source
nor the destination. Transfers can be requested in three modes: auto-request, external request, and
on-chip module request. The request mode is selected with the RS3–RS0 bits in the DMA channel
control registers 0–3 (CHCR0–CHCR3).
Auto-Request Mode: When there is no transfer request signal from an external source, as in a
memory-to-memory transfer or a transfer between memory and an on-chip supporting module
unable to request a transfer, the auto-request mode allows the DMAC to automatically generate a
transfer request signal internally. When the DE bits in CHCR0–CHCR3 and the DME bit in
DMAOR are set to 1, the transfer begins (so long as the TE bits in CHCR0–CHCR3 and the NMIF
and AE bits in DMAOR are all 0).
External Request Mode: In this mode a transfer is performed in response to a request signal
(DREQ) of an external device. Choose one of the modes shown in table 9.3 according to the
application system. When this mode is selected, if DMA transfer is enabled (DE = 1, DME = 1,
TE = 0, NMIF = 0, AE = 0), a transfer is performed upon a request at the DREQ input. Choose to
detect DREQ by either the falling edge or low level of the signal input with the DS bit in CHCR0–
CHCR3 (DS = 0 specifies level detection, DS = 1 specifies edge detection). The source of the
transfer request does not have to be the data transfer source or destination.
Table 9.3 Selecting External Request Modes with the RS Bits
RS3 RS2 RS1 RS0 Address Mode Source
Destination
0
0
0
0
Dual address
Any*
mode
Any*
0
0
1
0
Single address External memory or External device with
mode
memory-mapped DACK
external device
0
0
1
1
Single address External device with External memory or
mode
DACK
memory-mapped
external device
Note: * External memory, memory-mapped external device, on-chip memory, on-chip supporting
module (excluding DMAC)
On-Chip Module Request: In this mode a transfer is performed in response to a transfer request
signal (interrupt request signal) of an on-chip module. The transfer request signals include the
receive data full interrupt (RXI) of the serial communication interface (SCI), the transmit data
empty interrupt (TXI) of the SCI, the input capture A/compare match A interrupt request (IMIA)
of the 16-bit integrated pulse timer (ITU), and the A/D conversion end interrupt (ADI) of the A/D
Rev. 7.00 Jan 31, 2006 page 194 of 658
REJ09B0272-0700