SH7052 datasheet(823/919 Pages) RENESAS

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23.2.4

Notes on Register Access

The method of writing to the module standby control register (MSTCR) is different from that of

ordinary registers to prevent inadvertent rewriting.

Be certain to use a word transfer instruction when writing data to MSTCR. Data cannot be written

by a byte transfer instruction. As shown in figure 23.1, set the upper byte to H'3C and transfer data

using the lower byte as write data.

Data can be read by the same method as for ordinary registers.

MSTCR is allocated to address H'FFFFF70A. Always use a byte transfer instruction to read data.

H'3C

Write data

Address:

When writing to MSTCR

H'FFFFF70A

Figure 23.1 Writing to MSTCR

23.3

Hardware Standby Mode

23.3.1

Transition to Hardware Standby Mode

The chip enters hardware standby mode when the

HSTBY pin or RES pin goes low. Hardware

standby mode reduces power consumption drastically by halting all SH7052F/SH7053F/SH7054F

functions. As the transition to hardware standby mode is made by means of external pin input, the

transition is made asynchronously, regardless of the current state of the

SH7052F/SH7053F/SH7054F, and therefore the chip state prior to the transition is not preserved.

However, on-chip RAM data is retained as long as the specified voltage is supplied. To retain on-

chip RAM data, clear the RAM enable bit (RAME) to 0 in the system control register (SYSCR)

before driving the

HSTBY pin low. See Appendix B Pin States for the pin states in hardware

standby mode.

23.3.2

Canceling Hardware Standby Mode

Hardware standby mode is canceled by means of the

HSTBY pin and RES pin. When HSTBY is

driven high while

RES is low, the clock oscillator starts running. The RES pin should be held low

long enough for clock oscillation to stabilize. When

RES is driven high, power-on reset exception

processing is started and a transition is made to the program execution state.

SH7052 Datasheet(PDF) 823 Page - Renesas Technology Corp