H8S2245 datasheet(246/818 Pages) RENESAS

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Section 7 Data Transfer Controller

Rev.3.00 Mar. 26, 2007 Page 204 of 772

REJ09B0355-0300

7.3.12

Examples of Use of the DTC

(1) Normal Mode

The first example shows how the DTC can be used to receive 128 bytes of data via the SCI.

[1] Set MRA to fixed source address (SM1 = SM0 = 0), incrementing destination address (DM1 =

1, DM0 = 0), normal mode (MD1 = MD0 = 0), and byte size (Sz = 0). The DTS bit can have

any value. Set MRB for one data transfer by one interrupt (CHNE = 0, DISEL = 0). Set the

SCI RDR address in SAR, the start address of the RAM area where the data will be received in

DAR, and 128 (H'0080) in CRA. CRB can be set to any value.

[2] Set the start address of the register information at the DTC vector address.

[3] Set the corresponding bit in DTCER to 1.

[4] Set the SCI to the appropriate receive mode. Set the RIE bit in SCR to 1 to enable the reception

complete (RXI) interrupt. Since the generation of a receive error during the SCI reception

operation will disable subsequent reception, the CPU should be enabled to accept receive error

interrupts.

[5] Each time reception of one byte of data ends on the SCI, the RDRF flag in SSR is set to 1, an

RXI interrupt is generated, and the DTC is activated. The receive data is transferred from RDR

to RAM by the DTC, and then DAR is incremented and CRA is decremented. The RDRF flag

is automatically cleared to 0.

[6] When CRA becomes 0 after the 128 data transfers have ended, the RDRF flag is held at 1, the

DTCE bit is cleared to 0, and an RXI interrupt request is sent to the CPU. The interrupt

handling routine should perform wrap-up processing.

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