FR60 MB91460E Series - Microcontrollers - Fujitsu

2. Standby RAM
MB91460E Series
MB91F467E containes a 16 KByte low-leakage RAM used as Standby RAM. The power supply of this RAM is
not switched off in Shutdown state.
The Standby RAM is located at addresses FFFAC000H to FFFAFFFH.
To access it, to the RAM must be enabled by setting RAMEN bit in SHDE register. RAMEN is initialized by
Software Reset (RST). If the RAM is to be accessed, make sure that no external bus Chip Select area overlaps
the Standby RAM addresses.
The bit RAMEN is written using CLKP, while the Standby RAM is accessed with CLKB. If CLKP is slower then
CLKB, make sure to have some wait time (at least 2 CLKP periods) between setting of RAMEN and first RAM
access.
For the Standby RAM, low-leakage macros have been implemented. Read and write acces are performed with
1 wait cycle.
3. Shutdown Registers
3.1. Notes About the Reset Signals
The following register description mentiones different reset signals, which are explained shortly here. For more
information, please refer to the MB91460 series hardware manual, “Chapter 9 Reset”.
• Settings Initialization Reset (INIT):
initializes all the device’s control and clock settings. INIT can be triggered
- by low level on external INITX pin
- by low level on external HSTX pin (no hardware standby pin available in MB91460E series)
- by Hardware Watchdog Timer
- by Clock Supervisor
- by Software Watchdog Timer
- by Low Voltage Detection
• Operation Initialization Reset (RST, “Software Reset”):
initializes CPU and peripherals and restarts the software. RST can be triggered
- by low level on external RSTX pin (not available in MB91460E series)
- by INIT (INIT always causes RST)
- by software (STCR.SRST=0)
• Shutdown Recovery: The Shutdown state is released when a valid recovery factor is found. Shutdown recovery
causes a Settings Initialization Reset (INIT) with some exceptions. For details, please refer to “Recovery from
shutdown mode” on page 88.
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