SH7760 Datasheet, PDF (329/1345 Pages) Renesas Technology Corp – SuperHTM RISC engine

10.5.16 Accessing Refresh Control Related Registers
RTCSR, RTCNT, RTCOR, and RFCR require that a specific code be appended to the data when it
is written to prevent data from being mistakenly overwritten by program overruns or other write
operations. Perform reads and writes using the following methods:
(1) Write to RTCSR, RTCNT, RTCOR, or RFCR
When writing to RTCSR, RTCNT, RTCOR, and RFCR, use only word transfer instructions.
They cannot be written to with byte transfer instructions.
When writing to RTCNT, RTCSR, or RTCOR, place B'10100101 in the upper byte and the
write data in the lower byte. When writing to RFCR, place B'101001 in the top six bits and the
write data in the remaining bits, as shown in figure 10.5.
15 14 13 12 11 10 9
RTCSR, RTCNT, _{1 0 1 0 0 1 0}
RTCOR
15 14 13 12 11 10 9
RFCR 1 0 1 0 0 1
87
1
87
65 4 3 2
Write data
65 4 3 2
Write data
10
10
Figure 10.5 Write to RTCSR, RTCNT, RTCOR, or RFCR
(2) Read from RTCSR, RTCNT, RTCOR, or RFCR
RTCSR, RTCNT, RTCOR, or RFCR should be read in 16-bit units. Each reserved bit is
always read as 0.
Rev. 1.0, 02/03, page 279 of 1294