MM58274CN-12 National Semiconductor, MM58274CN-12 Datasheet - Page 6

• Manufacturer Part Number: MM58274CN-12
• Manufacturer: National Semiconductor

Specifications of MM58274CN-12

• Bus Type: Parallel
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 4.5V
• Operating Temperature Classification: Industrial
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Pin Count: 16
• Mounting: Through Hole
• Date Format: DW:DM:M:Y
• Time Format: HH:MM:SS:hh
• Lead Free Status / RoHS Status: Not Compliant

Functional Description
device which are synchronously clocked by this signal All
time data and data-changed flag change on the falling edge
of the clock setting pulse
Data-Changed Flag
The data-changed flag is set by the clock setting pulse to
indicate that the time data has been altered since the clock
was last read This flag occupies bit 3 of the control register
where it can be tested by the processor to sense data-
changed It will be reset by a read of the control register
See the section ‘‘Methods of Device Operation’’ for sug-
gested clock reading techniques using this flag
Seconds Counters
There are three counters for seconds
a) tenths of seconds
b) units of seconds
c) tens of seconds
The registers are accessed at the addresses shown in Ta-
ble I The tenths of seconds register is reset to 0 when the
clock start stop bit (bit 2 of the control register) is set to
logic 1 The units and tens of seconds are set up by the
processor giving time setting to the nearest second All
three registers can be read by the processor for time output
Minutes Counters
There are two minutes counters
a) units of minutes
b) tens of minutes
Both registers may be read to or written from as required
Hours Counters
There are two hours counters
a) units of hours
b) tens of hours
10 Units Months
11 Tens Months
12 Units Years
13 Tens Years
14 Day of Week
15 Clock Setting
0 Control Register
1 Tenths of Seconds
2 Units Seconds
3 Tens Seconds
4 Units Minutes
5 Tens Minutes
6 Unit Hours
7 Tens Hours
8 Units Days
9 Tens Days
Register Selected
Interrupt Registers
TABLE I Address Decoding of Real-Time Clock Internal Registers
AD3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
(Continued)
AD2
Address (Binary)
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
AD1
6
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Both counters may be accessed for read or write operations
as desired
The tens of hours register has only one active bit and the
top three bits are set to logic 0 Data bit 1 of the clock
setting register is the AM PM indicator logic 0 indicating
AM logic 1 for PM
Bit 0 of the clock setting register must be written to 0 for
correct 12 hour operation
Days Counters
There are two days counters
a) units of days
b) tens of days
The days counters will count up to 28 29 30 or 31 depend-
ing on the state of the months counters and the leap year
counter The microprocessor has full read write access to
these registers
Months Counters
There are two months counters
a) units of months
b) tens of months
Both these counters have full read write access
Years Counters
There are two years counters
a) units of years
b) tens of years
Both these counters have full read write access The years
will count up to 99 and roll over to 00
AD0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
(Hex)
A
B
C
D
0
1
2
3
4
5
6
7
8
9
E
F
Split Read and Write
Read Only
R W
R W
R W
R W
R W
R W
R W
R W
R W
R W
R W
R W
R W
R W
Access