Notes On Power Switching Function Is Used; Related Registers Of The Backup Power Supply Switching Function - Epson RX8900SA/CE Applications Manual

RX8900 SA / CE

8.8.4. Notes on power switching function is used

1.Please make VDD = 0V, when you backup.
If the VDD voltage is lower than VACCSW(2), there is an unnecessary current flows through the input and output
circuit. The transition to the backup from NORMAL state, please set to VDD = 0V promptly. Also, when returning from a
backup, please set to VDD level of desired promptly.
2. Between the external battery and VBAT terminal, please set limits resistance.
3. Even after that became VDD = 0V, VDD voltage detection to the next period, VBAT-VDD between PMOS switch
remains on. Because VDD voltage detection operate every second, between VBAT-VDD become a short-circuit
condition about one second

8.8.5. Related registers of the backup power supply switching function

Address
18 Backup Function
VDETOFF SWOFF
0
1
1
Function bit 7

BKSMP1 BKSMP0
0 0
0 1
-
1 0
1 1
0 - -
1 - -
bit 6 bit 5 bit 4
  
VDD monitor
(VDET3)
Intermittent ON Intermittent OFF
2msec
Intermittent ON Intermittent OFF
16msec
Intermittent ON Intermittent OFF
128msec
Intermittent ON Intermittent OFF
256msec
Always OFF
Always OFF
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bit 3 bit 2 bit 1
VDET
SWOFF BKSMP1
OFF
VDETOFF SWOFF
[default]
2msec
16msec
128msec
256msec
Always ON
Always OFF
ETM45E-01
bit 0
BKSMP0