Control Registers; Rtca Control Register (Low Byte) - Epson S1C31W74 Technical Manual

10 REAL-TIME CLOCK (RTCA)
RTCA provides interrupt enable bits corresponding to each interrupt flag. An interrupt request is sent to the CPU
only when the interrupt flag, of which interrupt has been enabled by the interrupt enable bit, is set. For more infor-
mation on interrupt control, refer to the "Interrupt" chapter.

10.6 Control Registers

RTCA Control Register (Low Byte)

Register name Bit
RTCACTLL 7
6
5
4
3
2
1
0
Bit 7 Reserved
Bit 6 RTCBSY
This bit indicates whether the counter is performing count-up operation or not.
1 (R): In count-up operation
0 (R): Idle (ready to rewrite real-time clock counter)
This bit goes 1 when performing 1-second count-up, +1 second correction, or 30-second correction. It
retains 1 for 1/256 second and then reverts to 0.
Bit 5 RTCHLD
This bit halts the count-up operation of the real-time clock counter.
1 (R/W): Halt real-time clock counter count-up operation
0 (R/W): Normal operation
Writing 1 to this bit halts the count-up operation of the real-time clock counter, this makes it possible
to read the counter value correctly without changing the counter. Write 0 to this bit to resume count-
up operation immediately after the counter has been read. Depending on these operation timings, the
+1 second correction may be executed after the count-up operation resumes. For more information on
the +1 second correction, refer to "Real-Time Clock Counter Operations."
Note: When the RTCACTLH.RTCTRMBSY bit = 1, the RTCACTLL.RTCHLD bit cannot be rewritten
to 1 (as fixed at 0).
Bit 4 RTC24H
This bit sets the hour counter to 24H mode or 12H mode.
1 (R/W): 24H mode
0 (R/W): 12H mode
This selection changes the count range of the hour counter. Note, however, that the counter value is
not updated automatically, therefore, it must be programmed again.
Note: Be sure to avoid writing to this bit when the RTCACTLL.RTCRUN bit = 1.
Bit 3 Reserved
Bit 2 RTCADJ
This bit executes the 30-second correction time adjustment function.
1 (W): Execute 30-second correction
0 (W): Ineffective
1 (R): 30-second correction is executing.
0 (R): 30-second correction has finished. (Normal operation)
10-6
Bit name Initial
– 0
RTCBSY 0
RTCHLD 0
RTC24H 0
– 0
RTCADJ 0
RTCRST 0
RTCRUN 0
Seiko Epson Corporation
Reset R/W
– R –
H0 R
H0 R/W Cleared by setting the
RTCACTLL.RTCRST bit to 1.
H0 R/W –
– R
H0 R/W Cleared by setting the
RTCACTLL.RTCRST bit to 1.
H0 R/W –
H0 R/W
S1C31W74 TECHNICAL MANUAL
Remarks
(Rev. 1.1)