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IT0: 128 Hz interrupt factor flag (FFFEH•D0)
IT1: 64 Hz interrupt factor flag (FFFEH•D1)
IT2: 32 Hz interrupt factor flag (FFFEH•D2)
IT3: 16 Hz interrupt factor flag (FFFEH•D3)
IT4:
8 Hz interrupt factor flag (FFFFH•D0)
IT5:
4 Hz interrupt factor flag (FFFFH•D1)
IT6:
2 Hz interrupt factor flag (FFFFH•D2)
IT7:
1 Hz interrupt factor flag (FFFFH•D3)
These flags indicate the status of the clock timer interrupt.
When "1" is read:
When "0" is read:
When "1" is written: Flag reset
When "0" is written: Invalid
The interrupt factor flags (IT0, IT1, IT2, IT3, IT4, IT5, IT6, IT7) correspond to the clock timer interrupts of
the respective frequencies (128 Hz, 64 Hz, 32 Hz, 16 Hz, 8 Hz, 4 Hz, 2 Hz, 1 Hz). The software can judge
from these flags whether there is a clock timer interrupt. However, even if the interrupt is masked, the flags
are set to "1" at the falling edge of the signal.
These flags are reset to "0" by writing "1" to them.
After an interrupt occurs, the same interrupt will occur again if the interrupt enabled state (I flag = "1") is
set or the RETI instruction is executed unless the interrupt factor flag is reset. Therefore, be sure to reset (write
"1" to) the interrupt factor flag in the interrupt service routine before shifting to the interrupt enabled state.
At initial reset, these flags are set to "0".
4.7.6 Programming notes
(1) Be sure to read timer data in the order of low-order data (TM0–TM3) then high-order data (TM4–TM7).
(2) The clock timer count clock does not synch with the CPU clock. Therefore, the correct value may not
be obtained depending on the count data read and count-up timings. To avoid this problem, the clock
timer count data should be read by one of the procedures shown below.
• Read the count data twice and verify if there is any difference between them.
• Temporarily stop the clock timer when the counter data is read to obtain proper data.
(3) After an interrupt occurs, the same interrupt will occur again if the interrupt enabled state (I flag = "1")
is set or the RETI instruction is executed unless the interrupt factor flag is reset. Therefore, be sure to
reset (write "1" to) the interrupt factor flag in the interrupt service routine before shifting to the interrupt
enabled state.
Interrupt has occurred
Interrupt has not occurred
SIC63616-(Rev. 1.0) NO. P83
3240-0412
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