
HITACHI 109
Bit:
15
14
13
12
11
10
9
8
Bit name:
—
—
—
—
—
—
—
—
Initial value:
0
—
0
—
0
—
0
—
0
—
0
—
0
—
0
—
R/W:
Bit:
7
6
5
4
3
2
1
0
Bit name:
CMF
CMIE
CKS2
CKS1
CKS0
—
—
—
Initial value:
0
0
0
0
0
0
—
0
—
0
—
R/W:
R/W
R/W
R/W
R/W
R/W
Bits 15–8 (reserved): These bits always read as 0.
Bit 7 (compare match flag (CMF)): CMF is a flag that indicates whether the values of RTCNT
and the refresh time constant register (RTCOR) match. When 0, the value of RTCNT and
RTCOR do not match; when 1, the value of RTCNT and RTCOR match.
Bit 7: CMF
Description
0
RTCNT does not equal the value of RTCOR (initial value)
To clear CMF, the CPU must read CMF after it has been set to 1, then write a
0 in this bit
1
Value RTCNT is equal to the value of RTCOR
Bit 6 (compare match interrupt enable (CMIE)): CMIE enables or disables the compare match
interrupt (CMI) generated when CMF is set to 1 in RTCSR (RTCNT value = RTCOR value).
When cleared to 0, CMI interrupt is disabled; when set to 1, it is enabled.
Bit 6: CMIE
Description
0
Compare match interrupt request (CMI) is disabled (initial value)
1
Compare match interrupt request (CMI) is enabled
Bits 5–3 (clock select bits 2–0 (CKS2–CKS0)): CKS2–CKS0 select the clock input to RTCNT
from among the seven types of clocks created by dividing the system clock (
φ
). When the input
clock is selected with the CKS2–CKS0 bits, RTCNT starts to increment.