Epson S1C63558 4.15.5 I/O memory of FSK demodulator, RDET: Ring detection bit (FF66H•D1), FSKON: FSK demodulator control register (FF66H•D3)

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (FSK Demodulator)

4.15.5 I/O memory of FSK demodulator

Table 4.15.5.1 shows the I/O address and control bits for the FSK demodulator.

Table 4.15.5.1 Control bits of FSK demodulator

Address		Register									Comment
	D3	D2	D1	D0	Name	Init ∗1	1		0
	FSKON	0	RDET	CDET	FSKON	0		On		Off	FSK demodulator On/Off
					0 ∗3	– ∗2					Unused
FF66H
	R/W		R		RDET	– ∗4	Ring		No Ring		Ring detection bit
					CDET	0	Carrier		No Carrier		Carrier detection bit
	0	0	RDETCP	CDETCP	0 ∗3	– ∗2					Unused
					0 ∗3	– ∗2					Unused
FF67H
	R		R/W		RDETCP	0					RDET comparison register
					CDETCP	0					CDET comparison register
	0	0	EIRDET	EICDET	0 ∗3	– ∗2					Unused
					0 ∗3	– ∗2					Unused
FFEAH
	R		R/W		EIRDET	0	Enable		Mask		Interrupt mask register (FSK demodulator ring detection)
					EICDET	0	Enable		Mask		Interrupt mask register (FSK demodulator carrier detection)
	0	0	IRDET	ICDET	0 ∗3	– ∗2		(R)		(R)	Unused
					0 ∗3	– ∗2	Yes			No	Unused
FFFAH
	R		R/W		IRDET	0	(W)		(W)		Interrupt factor flag (FSK demodulator ring detection)
					ICDET	0	Reset		Invalid		Interrupt factor flag (FSK demodulator carrier detection)

*1 Initial value at initial reset

*2 Not set in the circuit

*3 Constantly "0" when being read

*4 Depends on the input status of the RDIN terminal

FSKON: FSK demodulator control register (FF66H•D3)

Turns the FSK demodulator ON and OFF.

When "1" is written: ON

When "0" is written: OFF

Reading: Valid

The FSK demodulator goes ON by writing "1" to FSKON. At the same time, the data input line of the serial interface (2) is switched from the P30 terminal to the FSK demodulator output. The P3x terminals function as general I/O port terminals regardless of the ESIFS setting.

When starting the FSK demodulator operation, the OSC3 oscillation circuit must be turned ON and the CPU operating clock must be switched to the OSC3 clock.

The FSK demodulator goes OFF by writing "0" to FSKON. The P3x terminals can be set to the I/O terminals used for the serial interface (2).

The FSK demodulator should be activated only when it is needed in order to decrease current consump- tion.

At initial reset, this register is set to "0".

RDET: Ring detection bit (FF66H•D1)

Indicates the ring detection status.

When "1" is read: Ring is detected

When "0" is read: Ring is not detected

Writing: Invalid

A ring signal is being input when RDIT is "1". When the ring input is completed, RDET returns to "0". This bit is dedicated for reading, so writing can not be done.

The bit valeu at initial reset depends on the input status of the RDIN terminal.

142 EPSON S1C63558 TECHNICAL MANUAL