Second/Minute/Hour Data Register - Fujitsu MB90420/5 (A) Series Hardware Manual

MB90420/5 (A) SERIES F

18.2.3 Second/Minute/Hour Data Register

The second/minute/hour data register stores time information. Seconds, minutes, and hours are expressed
in binary.
When these registers are read, the counter is simply restored to its original value. However, these registers
involve writes; after the UPDT bit is set to 1, write data is loaded into each counter.
n Second/minute/hour data register
Second data register
Address: 00395D
H
Read/write
Initial value
Minute data register
Address: 00395E
H
Read/write
Initial value
Hour data register
Address: 00395F
H
Read/write
Initial value
Since the second/minute/hour data register has three types of byte registers, check that the values obtained
from the second/minute/hour data register are consistent.
For example, when a value of 1 hour 59 minutes 59 seconds is obtained, it might be 0 hour 59 minutes 59
seconds or 1 hour 0 minute 0 second or 2 hours 0 minute 0 second.
Similarly, when the MCU operating clock is half the oscillation clock (when PLL stopped), values read from
these registers might be incorrect due to the synchronization of the read and counter operations.
Consequently, when using the second/minute/hour data register, read instructions should be triggered by
second interrupts.
2
MC-16LX FAMILY 16-BIT MICROCONTROLLERS HARDWARE MANUAL
bit 15 bit 14 bit 13
–– –– S5
— — (R/W)
— — (X)
bit 7 bit 6 bit 5
–– –– M5
— — (R/W)
— — (X)
bit 15 bit 14 bit 13
–– –– ––
— — —
— — —
18-8
bit 12 bit 11 bit 10
S4 S3 S2
(R/W) (R/W) (R/W)
(X) (X) (X)
bit 4 bit 3 bit 2
M4 M3 M2
(R/W) (R/W) (R/W)
(X) (X) (X)
bit 12 bit 11 bit 10
H4 H3 H2
(R/W) (R/W) (R/W)
(X) (X) (X)
Bit No.
bit 9 bit 8
S1 S0 WTSR
(R/W) (R/W)
(X) (X)
Bit No.
bit 1 bit 0
M1 M0 WTMR
(R/W) (R/W)
(X) (X)
Bit No.
bit 9 bit 8
H1 H0
WTHR
(R/W) (R/W)
(X) (X)