Programming Notes - Epson S1C63558 Technical Manual

ID: Interrupt factor flag (FFF9H•D0)
Indicates the dialing interrupt generation status.
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 flag ID is set to "1" when a dialing interrupt factor occurs (when a dialing output, pause
or flash cycle is completed). After executing a dialing function (dialing number, pause, flash), this flag
must be reset. Otherwise, the next dialing function can not be executed.
The interrupt factor flag is reset to "0" by writing "1".
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, this flag is set to "0".

4.14.11 Programming notes

(1) It is necessary to turn the OSC3 oscillation on prior to a dialing operation in tone mode because the
tone mode uses the OSC3 (3.58 MHz) clock. However it increases current consumption. Therefore,
turn the OSC3 oscillation off after finishing the dialling operation in tone mode.
(2) Do not write "0" (0000B) to the IDP, FTS, PTS or TCD (in pulse mode) registers because it may cause a
malfunction.
(3) The pause function control bit PAUSE (FF14H•D1) and the flash function control bit FLASH
(FF14H•D0) are write-only, so software cannot control these functions (on address FF14H) using an
ALU instruction (AND, OR ...). Furthermore, be aware that the pause function or the flash function is
canceled when "0" is written to the PAUSE bit (FF14H•D1) or the FLASH bit (FF14H•D0).
(4) 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.
S1C63558 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Telephone Function)
EPSON
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