HD6432621 Hitachi, HD6432621 Datasheet - Page 711

• Manufacturer Part Number: HD6432621
• Description: (HD64F262x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

19.12
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
(3) Standby mode: All flash memory circuits are halted, and the flash memory cannot be read or
States (2) and (3) are flash memory power-down states. Table 19-22 shows the correspondence
between the operating states of the LSI and the flash memory.
Table 19-22 Flash Memory Operating States
LSI Operating State
High-speed mode
Medium-speed mode
Sleep mode
Subactive mode
Subsleep mode
Watch mode
Software standby mode
Hardware standby mode
19.12.1 Note on Power-Down States
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.
read when the LSI is operating on the subclock.
written to.
Flash Memory and Power-Down States
Flash Memory Operating State
Normal mode (read/write)
When PDWND = 0: Power-down mode (read-only)
When PDWND = 1: Normal mode (read-only)
Standby mode
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