CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Telephone Function)

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

EPSON

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