HD64F2638F20J Datasheet, PDF (838/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 21A ROM
(H8S/2636 Group)
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
21A.14 Flash Memory and Power-Down States
In addition to its normal operating state, the flash memory has power-down states in which power
consumption is reduced by halting part or all of the internal power supply circuitry.
There are three flash memory operating states:
(1) Normal operating mode: The flash memory can be read and written to.
(2) Power-down mode: Part of the power supply circuitry is halted, and the flash memory can be
read when the LSI is operating on the subclock*.
(3) Standby mode: All flash memory circuits are halted, and the flash memory cannot be read or
written to.
States (2) and (3) are flash memory power-down states. Table 21A-14 shows the correspondence
between the operating states of the LSI and the flash memory.
Table 21A-14 Flash Memory Operating States
LSI Operating State
Flash Memory Operating State
High-speed mode
Medium-speed mode
Sleep mode
Subactive mode^*
Subsleep mode^*
Watch mode^*
Software standby mode
Hardware standby mode
Normal mode (read/write)
When PDWND = 0: Power-down mode (read-only)
When PDWND = 1: Normal mode (read-only)
Standby mode
Note: * Subclock functions (subactive mode, subsleep mode, and watch mode) are available in the
U-mask version only.
These functions cannot be used with the other versions.
21A.14.1 Notes on Power-Down States
1. When the flash memory is in a power-down state, part or all of the internal power supply
circuitry is halted. Therefore, a power supply circuit stabilization period must be provided
when returning to normal operation. When the flash memory returns to its normal operating
state from a power-down state, bits STS2 to STS0 in SBYCR must be set to provide a wait
time of at least 20 µs (power supply stabilization time), even if an oscillation stabilization
period is not necessary.
Page 788 of 1458
REJ09B0103-0800 Rev. 8.00
May 28, 2010