Epson RX-8801SA/JE bit, bit, bit, bit, bit, bit, bit, bit, TEST, WADA, USEL, TEST, Data, USEL, Data, tRTN, FSEL1, FSEL0, TSEL1, TSEL0, FSEL1, FSEL0, TSEL1, TSEL0, 500 ms

RX − 8801 SA / JE

8.2.4. Extension register (Reg-D)

Address	Function	bit 7	bit 6	bit 5	bit 4	bit 3	bit 2	bit 1	bit 0
D	Extension Register	TEST	WADA	USEL	TE	FSEL1	FSEL0	TSEL1	TSEL0
	(Default)	(0)	(−)	(−)	(−)	(0)	(0)	(−)	(−)

∗1) The default value is the value that is read (or is set internally) after powering up from 0 V. ∗2) "o" indicates write-protected bits. A zero is always read from these bits.

∗3) "−" indicates a default value is undefined.

•This register is used to specify the target for the alarm function or time update interrupt function and to select or set operations such as fixed-cycle timer operations.

1)TEST bitThis is the manufacturer's test bit. Its value should always be "0".Be careful to avoid writing a "1" to this bit when writing to other bits.

∗If a "1" is inadvertently written to this TEST bit, there is a safety function where by this bit will be automatically cleared to zero when a STOP condition or Repeated START condition is received or when the 0.95-second bus timeout function operates.

TEST	Data		Description
Write/Read	0	Normal operation mode	∗ Default

1Setting prohibited (manufacturer's test bit)2)WADA ( Week Alarm/Day Alarm ) bit

This bit is used to specify either WEEK or DAY as the target of the alarm interrupt function. Writing a "1" to this bit specifies DAY as the comparison object for the alarm interrupt function. Writing a "0" to this bit specifies WEEK as the comparison object for the alarm interrupt function.

3) USEL ( Update Interrupt Select ) bit

This bit is used to specify either "second update" or "minute update" as the update generation timing of the time update interrupt function.

USEL	Data	update interrupts		Auto reset time
				tRTN
Write/Read	0	second update	∗ Default	500 ms
	1	minute update		7.813 ms

4) TE ( Timer Enable ) bit

This bit controls the start/stop setting for the fixed-cycle timer interrupt function.

Writing a "1" to this bit specifies starting of the fixed-cycle timer interrupt function (a countdown starts from a preset value).

Writing a "0" to this bit specifies stopping of the fixed-cycle timer interrupt function.

5) FSEL0,1 ( FOUT frequency Select 0, 1 ) bitsThe combination of these two bits is used to set the FOUT frequency.

FSEL0,1	FSEL1	FSEL0	FOUT frequency
	(bit 3)	(bit 2)
	0	0	32768 Hz Output	∗ Default
Write/Read	0	1	1024 Hz Output
	1	0	1 Hz Output
	1	1	32768 Hz Output

6) TSEL0,1 ( Timer Select 0, 1 ) bits

The combination of these two bits is used to set the countdown period (source clock) for the fixed-cycle timer interrupt function (four settings can be made).

TSEL0,1	TSEL1	TSEL0	Source clock
	(bit 1)	(bit 0)
	0	0	4096	Hz	/Once per 244.14 μs
Write/Read	0	1	64	Hz	/ Once per 15.625 ms
	1	0	"Second" update		/Once per second
	1	1	"Minute" update		/Once per minute

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