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Rev. 2.0, 09/02, page 189 of 732
Table 10.10 Transfer Conditions and Register Set Values for Transfer between External
Memory and SCI1 Transmit Side
Transfer Conditions
Register
Value
Transfer source: external memory
SAR_3
H'00400000
Value stored in address H'00400000
—
H'00450000
Value stored in address H'00450000
—
H'55
Transfer destination: on-chip SCI1 (TDR1)
DAR_3
H'FFFF81B3
Transfer count: 10 times
DMATCR_3
H'0000000A
Transfer source address: incremented
CHCR_3
H'00011E01
Transfer destination address: fixed
Transfer request source: SCI1 (TDR1)
Bus mode: cycle steal
Transfer unit: byte
Interrupt request not generated at end of transfer
Channel priority ranking: 0
>
1
>
2
>
3
DMAOR
H'0001
When indirect address mode is on, the data stored in the address established in SAR is not used as
the transfer source data. In the case of indirect addressing, the value stored in the SAR address is
read, then that value is used as the address and the data read from that address is used as the
transfer source data, then that data is stored in the address designated by the DAR.
In the table 10.10 example, when a transfer request from the TDR_1 of SCI_1 is generated, a read
of the address located at H'00400000, which is the value set in SAR_3, is performed first. The data
H'00450000 is stored at this H'00400000 address, and the DMAC first reads this H'00450000
value. It then uses this read value of H'00450000 as an address and reads the value of H'55 that is
stored in the H'00450000 address. It then writes the value H'55 to the address H'FFFF81B3
designated by DAR_3 to complete one indirect address transfer.
With indirect addressing, the first executed data read from the address established in SAR_3
always results in a longword size transfer regardless of the TS0, TS1 bit designations for transfer
data size. However, the transfer source address fixed and increment or decrement designations are
as according to the SM0, SM1 bits. Consequently, despite the fact that the transfer data size
designation is byte in this example, the SAR_3 value at the end of one transfer is H'00400004. The
write operation is exactly the same as an ordinary dual address transfer write operation.