HD64F2145 datasheet(192/829 Pages) RENESAS

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Rev. 2.0, 08/02, page 152 of 788

7.7

Examples of Use of DTC

7.7.1

Normal Mode

An example is shown in which the DTC is used to receive 128 bytes of data via the SCI.

1. Set MRA to a 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 the reception of one byte of data has been completed 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. DAR is incremented and CRA is decremented.

The RDRF flag is automatically cleared to 0.

6. When CRA becomes 0 after 128 data transfers have been completed, 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 will perform wrap-up processing.

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