SH7730 Datasheet, PDF (491/1188 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7780 Series

Section 12 Direct Memory Access Controller (DMAC)
12.4.5 Repeat Mode Transfer
In a repeat mode transfer, a DMA transfer is repeated without specifying the transfer settings
every time before executing a transfer.
Using a repeat mode transfer with the half end function allows a double buffer transfer executed
virtually. Following processings can be executed effectively by using a repeat mode transfer. As
an example, operation of receiving voice data from the VOICE CODEC and compressing it is
explained.
In the following example, processing of compressing 40-word voice data every data reception is
explained. In this case, it is assumed that voice data is received by means of SIOF.
1. DMAC settings
• Set address of the SIOF receive data register in SAR
• Set address of an internal memory data store area in DAR
• Set TCR to 80 (H'50)
• Satisfy the following settings of CHCR
Bits RPT[2:0] = B'010: Repeat mode (use DAR as a repeat area)
Bit HIE = B'1: TCR/2 interrupt generated
Bits DM[1:0] = B'01: DAR incremented
Bits SM[1:0] = B'00: SAR fixed
Bit IE = B'1: Interrupt enabled
Bit DE = B'1: DMA transfer enabled
• Set such as bits TB and TS[3:0] according to use conditions
• Set bits CMS[1:0] and PR[1:0] in DMAOR according to use conditions and set the DME bit to
B'1
2. Voice data is received and then transferred by SIOF/DMAC
3. TCR is decreased to half of its initial value and an interrupt is generated
Read CHCR to confirm that the HE bit is set to 1 by an interrupt processing, and compress 40-
word voice data from the address set in DAR.
4. TCR is cleared to 0 and an interrupt is generated
Read CHCR to confirm that the TE bit is set to 1 by an interrupt processing, and compress 40-
word voice data from the address set in DAR + 40. After this operation, the value of DARB is
copied to DAR in DMAC and initialized, and the value of TCRB is copied to TCR and
initialized to 80.
Rev. 1.00 Sep. 19, 2007 Page 443 of 1136
REJ09B0359-0100