M41ST87YMX6TR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
M41ST87YMX6TR
STMicroelectronics
'M41ST87YMX6TR' PDF : 42 Pages View PDF
M41ST87Y, M41ST87W
Setting Alarm Clock Registers
Address locations 0Ah-0Eh contain the alarm set-
tings. The alarm can be configured to go off at a
prescribed time on a specific month, date, hour,
minute, or second, or repeat every year, month,
day, hour, minute, or second. It can also be pro-
grammed to go off while the M41ST87Y/W is in the
battery back-up to serve as a system wake-up call.
Bits RPT5–RPT1 put the alarm in the repeat mode
of operation. Table 8., page 28 shows the possible
configurations. Codes not listed in the table default
to the once per second mode to quickly alert the
user of an incorrect alarm setting.
When the clock information matches the alarm
clock settings based on the match criteria defined
by RPT5–RPT1, the AF (Alarm Flag) is set. If AFE
(Alarm Flag Enable) is also set, the alarm condi-
tion activates the IRQ/OUT pin as shown in Figure
25., page 29. To disable alarm, write '0' to the
Alarm Date Register and to RPT5–RPT1.
Note: If the address pointer is allowed to incre-
ment to the Flag Register address, an alarm con-
Figure 24. Alarm Interrupt Reset Waveform
dition will not cause the Interrupt/Flag to occur until
the address pointer is moved to a different ad-
dress. It should also be noted that if the last ad-
dress written is the “Alarm Seconds,” the address
pointer will increment to the Flag address, causing
this situation to occur.
The IRQ/OUT output is cleared by a READ to the
Flags Register. A subsequent READ of the Flags
Register is necessary to see that the value of the
Alarm Flag has been reset to '0.'
The IRQ/OUT pin can also be activated in the bat-
tery back-up mode. The IRQ/OUT will go low if an
alarm occurs and both ABE (Alarm in Battery
Back-up Mode Enable) and AFE are set. The ABE
and AFE Bits are reset during power-up, therefore
an alarm generated during power-up will only set
AF. The user can read the Flag Register at system
boot-up to determine if an alarm was generated
while the M41ST87Y/W was in the deselect mode
during power-up. Figure 25., page 29 illustrates
the back-up mode alarm timing.
0Eh
0Fh
ACTIVE FLAG
IRQ/OUT
Table 8. Alarm Repeat Modes
RPT5
RPT4
1
1
1
1
1
1
1
1
1
0
0
0
RPT3
1
1
1
0
0
0
RPT2
1
1
0
0
0
0
10h
HIGH-Z
AI07086
RPT1
1
0
0
0
0
0
Alarm Setting
Once per Second
Once per Minute
Once per Hour
Once per Day
Once per Month
Once per Year
28/42
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