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Page - 9 MQ372-02
8.2.3. Flag register (Reg-E)
Address Function bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
Flag register
!
!
UF TF AF
!
VLF
!
E
(Default) (0) (0)
(−) (−) (−)
(0) (1) (0)
∗1)
The default value is the value that is read (or is set internally) after powering up from 0 V.
∗2)
"o" indicates write-protected bits. A zero is always read from these bits.
∗3)
"−" indicates a default value is undefined.
• This register is used to detect the occurrence of various interrupt events and reliability problems in internal data.
1) UF (Update Flag) bit
If set to "0" beforehand, this flag bit's value changes from "0" to 1" when a time update interrupt event has
occurred. Once this flag bit's value is "1", its value is retained until a "0" is written to it.
∗
For details, see "8.4. Time Update Interrupt Function".
2) TF (Timer Flag) bit
If set to "0" beforehand, this flag bit's value changes from "0" to 1" when a fixed-cycle timer interrupt event has
occurred. Once this flag bit's value is "1", its value is retained until a "0" is written to it.
∗
For details, see "8.3. Fixed-cycle Timer Interrupt Function".
3) AF (Alarm Flag) bit
If set to "0" beforehand, this flag bit's value changes from "0" to 1" when an alarm interrupt event has occurred.
Once this flag bit's value is "1", its value is retained until a "0" is written to it.
∗
For details, see "8.5. Alarm Interrupt Function".
4) VLF (Voltage Low Flag) bit
This flag bit indicates the retained status of clock operations or internal data. Its value changes from "0" to "1"
when data loss occurs, such as due to a supply voltage drop. Once this flag bit's value is "1", its value is retained
until a "0" is written to it.
This bit's value is "1" after powering up from 0 V.
VLF
Data Description
0 The VLF bit is cleared to zero to prepare for the next status detection.
Write
1 This bit is invalid after a "1" has been written to it.
0
Data loss is not detected.
Read
1
Data loss is detected.
All registers must be initialized.
(This setting is retained until a "zero" is written to this bit.)