S1C63558 TECHNICAL MANUAL
EPSON
143
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (FSK Demodulator)
CDET: Carrier detection bit (FF66H•D0)
Indicates the carrier detection status.
When "1" is read: Carrier is detected
When "0" is read: Carrier is not detected
Writing: Invalid
CDET goes "1" when a carrier is input. When the carrier is stopped, CDET returns to "0". This bit is
dedicated for reading, so writing can not be done.
At initial reset, this bit is set to "0".
RDETCP: RDET comparison register (FF67H•D1)
Sets a generation condition for the ring detection interrupt.
When "1" is written: RDET falling edge
When "0" is written: RDET rising edge
Reading: Valid
When RDETCP is set to "1", the ring detection interrupt is generated at the falling edge of the RDET
signal. When RDETCP is "0", the interrupt is generated at the rising edge.
At initial reset, this register is set to "0".
CDETCP: CDET comparison register (FF67H•D0)
Sets a generation condition for the carrier detection interrupt.
When "1" is written: CDET falling edge
When "0" is written: CDET rising edge
Reading: Valid
When CDETCP is set to "1", the carrier detection interrupt is generated at the falling edge of the CDET
signal. When CDETCP is "0", the interrupt is generated at the rising edge.
At initial reset, this register is set to "0".
EIRDET, EICDET: Interrupt mask registers (FFEAH•D1, D0)
Enables or disables the generation of an interrupt for the CPU.
When "1" is written: Enabled
When "0" is written: Disabled
Reading: Valid
EIRDET and EICDET are interrupt mask registers that respectively correspond to the interrupt factors for
ring detection and carrier detection. Interrupts set to "1" are enabled and interrupts set to "0" are disabled.
At initial reset, these registers are set to "0".
IRDET, ICDET: Interrupt factor flags (FFFAH•D1, D0)
Indicates the FSK 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
IRDET and ICDET are interrupt factor flags that respectively correspond to the interrupts for ring
detection and carrier detection, and are set to "1" by generation of each factor.
When set in this manner, if the corresponding interrupt enable mask is set to "1" and the CPU is set to
interrupt enabled status (I flag = "1"), an interrupt will be generated to the CPU.
Regardless of the interrupt mask register setting, the interrupt factor flag will be set to "1" by the occur-
rence of an interrupt generation condition.
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