SH7021 datasheet(132/509 Pages) RENESAS

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114 RENESAS

Bit 12: PCHK1

Bit 11: PCHK0

Description

Parity not checked and not generated (initial value)

Parity checked and generated only in DRAM area

Parity checked and generated in DRAM area and area 2

Reserved

•

Bits 10–0 (reserved): These bits always read as 0. The write value should always be 0.

8.2.11

Notes on Register Access

RCR, RTCSR, RTCNT, and RTCOR differ from other registers in being more difficult to write.

Data requires a password when it is written. This prevents data from being mistakenly overwritten

by program overruns and the like.

Writing to RCR, RTCSR, RTCNT, and RTCOR: Use only word transfer instructions. You

cannot write with byte transfer instructions. As figure 8.2 shows, when writing to RCR, place

H'5A in the upper byte and the write data in the lower byte. When writing to RTCSR, place H'A5

in the upper byte and the write data in the lower byte. When writing to RTCNT, place H'69 in the

upper byte and the write data in the lower byte. When writing to RTCOR, place H'96 in the upper

byte and the write data in the lower byte. These transfers write data in the lower byte to the

respective registers. If the upper byte differs from the above passwords, no writing occurs.

H'5A

Write data

RCR

H'A5

Write data

RTCSR

H'69

Write data

RTCNT

H'96

Write data

RTCOR

Figure 8.2 Writing to RCR, RTCSR, RTCNT, and RTCOR

Reading from RCR, RTCSR, RTCNT, and RTCORP: These registers are read like other

registers. They can be read by byte and word transfer instructions. If read by word transfer, the

value of the upper eight bits is H'00.

SH7021 Datasheet(PDF) 132 Page - Renesas Technology Corp