RX8804CE
Page - 29
ETM59E-05
8.7. Time Update Interrupt Function
8.7.1. Time Update Interrupt Function
The time update interrupt function generates interrupt events at one-second or one-minute intervals, according to
the timing of the internal clock.
When an interrupt event occurs, the UF bit value becomes “1” and the /INT pin goes to low level to indicate that
an event has occurred. (However, when a wakeup timer interrupt event has been generated, low-level output
from the /INT
pin occurs only when the value of the control register's UIE bit is “1”. This /INT status is
automatically cleared (/INT status changes from low level to Hi-Z) earliest 7.813
ms (fixed value) after the
interrupt occurs.
/INT operation
example
UIE =
"
1
"
7.813ms
Min.
period
UIE
=
"
1
"
→
"
0
"
Figure 18 Update Interrupt Function
8.7.2. Related Registers for Time Update Interrupt Functions
Table 52 Update Interrupt Function Register
Address
Function
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
0D
Control 1
TEST
WADA
USEL
TE
FSEL1
FSEL0
TSEL1
TSEL0
0E
Flag Register
UF
TF
AF
VLF
VDET
0F
Control 2
CSEL1
CSEL0
UIE
TIE
AIE
RESET
)
o indicates write-protected bits. A zero is always read from these bits.
Before entering settings for operations, we recommend writing a “0” to the UIE bit to prevent hardware interrupts
from occurring inadvertently while entering settings.
When the RESET bit value is 1
time update interrupt events do not occur.
Although the time update interrupt function cannot be fully stopped, if
“0” is written to the UIE bit, the time update
interrupt function can be prevented from changing the /INT pin status to low.
1) USEL (Update Interrupt Select) bit
This bit is used to select "second" update or "minute" update as the timing for generation of time update interrupt
events.
Table 53 USEL bit
USEL
Data
update interrupts
Auto reset time t
RTN
Write / Read
0
second update
Default
500 ms
1
minute update
7.813 ms Min.
2) UF (Update Flag) bit
Once it has been set to "0", this flag bit value changes from "0" to "1" when a time update interrupt event occurs.
When this flag bit = "1" its value is retained until a "0" is written to it.
Table 54 UF bit
UF
Data
Description
Write
0
The UF bit is cleared to zero to prepare for the next detection.
In time update interruption, even if UF is cleared, INT is not released.
1
Invalid (writing a 1 will be ignored)!
Read
0
Time update interrupt events are not detected
1
Time update interrupt events are detected
(The result is retained until this bit is cleared to zero)
3) UIE (Update Interrupt Enable) bit