SH7080 Datasheet, PDF (269/1644 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 8 Data Transfer Controller (DTC)
8.7 Examples of Use of the DTC
8.7.1 Normal Transfer Mode
An example is shown in which the DTC is 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 transfer mode (MD1 = MD0 = 0), and byte size (Sz1 = Sz0 = 0). The
DTS bit can have any value. Set MRB for one data transfer by one interrupt (CHNE = 0,
DISEL = 0). Set the RDR address of the SCI 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 transfer information for an RXI interrupt 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 receive
end (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. 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. Termination
processing should be performed in the interrupt handling routine.
8.7.2 Chain Transfer when Counter = 0
By executing a second data transfer and performing re-setting of the first data transfer only when
the counter value is 0, it is possible to perform 256 or more repeat transfers.
An example is shown in which a 128-kbyte input buffer is configured. The input buffer is assumed
to have been set to start at lower address H'0000. Figure 8.19 shows the chain transfer when the
counter value is 0.
1. For the first transfer, set the normal transfer mode for input data. Set the fixed transfer source
address, CRA = H'0000 (65,536 times), CHNE = 1, CHNS = 1, and DISEL = 0.
2. Prepare the upper 8-bit addresses of the start addresses for 65,536-transfer units for the first
data transfer in a separate area (in ROM, etc.). For example, if the input buffer is configured at
addresses H'200000 to H'21FFFF, prepare H'21 and H'20.
Rev. 3.00 May 17, 2007 Page 211 of 1582
REJ09B0181-0300