Programming Notes - Epson S1C63656 Technical Manual

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Clock Timer)
TMRUN: Clock timer RUN/STOP control register (FF74H•D0)
Controls RUN/STOP of the clock timer.
When "1" is written: RUN
When "0" is written: STOP
Reading: Valid
The clock timer enters the RUN status when "1" is written to the TMRUN register, and the STOP status
when "0" is written. In the STOP status, the timer data is maintained until the next RUN status or the
timer is reset. Also, when the STOP status changes to the RUN status, the data that is maintained can be
used for resuming the count.
At initial reset, this register is set to "0".
EIT0: 32 Hz interrupt mask register (FFE5H•D0)
EIT1: 8 Hz interrupt mask register (FFE5H•D1)
EIT2: 2 Hz interrupt mask register (FFE5H•D2)
EIT3: 1 Hz interrupt mask register (FFE5H•D3)
EIT4: 16 Hz interrupt mask register (FFE9H•D0)
These registers are used to select whether to mask the clock timer interrupt.
When "1" is written: Enabled
When "0" is written: Masked
Reading: Valid
The interrupt mask registers (EIT0, EIT1, EIT2, EIT3, EIT4) are used to select whether to mask the inter-
rupt to the separate frequencies (32 Hz, 8 Hz, 2 Hz, 1 Hz, 16 Hz).
At initial reset, these registers are set to "0".
IT0: 32 Hz interrupt factor flag (FFF5H•D0)
IT1: 8 Hz interrupt factor flag (FFF5H•D1)
IT2: 2 Hz interrupt factor flag (FFF5H•D2)
IT3: 1 Hz interrupt factor flag (FFF5H•D3)
IT4: 16 Hz interrupt factor flag (FFF9H•D0)
These flags indicate the status of the clock timer interrupt.
When "1" is read: Interrupt has occurred
When "0" is read: Interrupt has not occurred
When "1" is written: Flag is reset
When "0" is written: Invalid
The interrupt factor flags (IT0, IT1, IT2, IT3, IT4) correspond to the clock timer interrupts of the respective
frequencies (32 Hz, 8 Hz, 2 Hz, 1 Hz, 16 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".

4.8.5 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) 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.
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EPSON
S1C63656 TECHNICAL MANUAL