MM58174AN National Semiconductor, MM58174AN Datasheet - Page 5

• Manufacturer Part Number: MM58174AN
• Description: IC MPU CLOCK CAL 16DIP +DATA
• Manufacturer: National Semiconductor
• Type: Clock/Calendarr

Specifications of MM58174AN

• Time Format: HH:MM:SS (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: Parallel
• Voltage - Supply: 2.2 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Memory Size: -
• Other names: *MM58174AN; 58174; MM58174

Figure 4 is an electrical representation of the crystal along
Circuit Description
DB3
DB3
X
Note Leap year counter rolls over on December 31
INTERRUPT SYSTEM
The interrupt output and its frequency of operation is en-
abled by writing to address 15 (see Table IIa) To ensure
correct operation the interrupt should be serviced within
16 6 ms
The interrupt is initialized by writing ‘‘0’’ to address 15 and
reading the interrupt i e reading at address 15 three times
Initialization must be performed at power on and also if the
interrupt is not serviced correctly within 16 6 ms
SERVICING THE INTERRUPT
In a typical system the open drain interrupt output is wired to
the processor interrupt system Hence when the interrupt
timer times out the interrupt output is pulled low and the
processor is interrupted
The processor may then reset the interrupt by utilizing the
following procedure
Read Address 15 three times
This resets the interrupt output and restarts the interrupt
timer when in the repeat mode
It is recommended that the interrupt output is connected to
a unique processor port
CRYSTAL PARAMETERS
with some typical values The 32 768 kHz crystal is an NT
CUT (tuning fork type) or XY BAR for use in a parallel reso-
nant Pierce oscillator
a
Mode Address 15 Write Mode
Function
No Interrupt
Int at 60 Sec Intervals
Int at 5 0 Sec Intervals
Int at 0 5 Sec Intervals
e
Mode Address 15 Read Mode
Interrupt Status
Reset
60 Sec Signal
5 0 Sec Signal
0 5 Sec Signal
Mode Address 13 Write Mode
Leap Year
Leap Year-1
Leap Year-2
Leap Year-3
16 6 ms
e
e
don’t care state
0 single interrupt
1 repeated interrupt
TABLE IIb Interrupt Read Back (Status)
TABLE IIa Interrupt Selection Data
TABLE III Years Status Register
DB3
1
0
0
0
DB3
X
X
X
X
DB3
0 1
0 1
0 1
X
DB2
(Continued)
0
1
0
0
DB2
0
1
0
0
DB2
0
1
0
0
DB1
DB1
0
0
1
0
23 59 59
0
0
1
0
DB1
0
0
1
0
DB0
DB0
DB0
0
0
0
1
0
0
0
1
0
0
0
1
5
DEVICE INITIALIZATION AND OSCILLATOR SETTING
When first installed or if the battery back-up has failed the
MM58174A will require to be properly initialized The follow-
ing sequence is a suggested flow of operations to achieve
this
1) Apply power
2) Write ‘‘0’’ to address 15
3) Read 3 times from
4) Write ‘‘0’’ on DB3 to
5) Write ‘‘0’’ on DB0 to
6) Set up timekeeping
7) Write ‘‘1’’ on DB0 to
8) Program and start
OSCILLATOR SETTING
Directly connecting a frequency meter to the Crystal Out pin
(14) will not allow correct frequency setting because of the
extra capacitive loading of the meter One possibility for set-
ting is to use a high impedance probe or a CMOS buffer to
keep the loading as low as possible (e g 100 x 2 pF probe)
Alternatively a buffered output of 16 384 kHz OSC 2 can
be produced on DB0 by applying the following procedure
1) Write a ‘‘1’’ on DB3 to
2) Write a ‘‘1’’ on DB0 to
3) Read at address 1 (tenths
4) Read at address 1 and
5) Adjust trimmer capacitor
There must be no extra activity on the RD line between
steps 3 and 4 or only the normal ‘‘Data Changed’’ signal will
be observed on the data bus Thus if the normal host proc-
essor system is being used to generate the chip waveforms
proper care must be taken
address 15
address 0
address 14
registers
address 14
interrupts
address 0
address 14
of secs)
HOLD the strobe LOW
FIGURE 4 Typical Crystal Parameters
Action
Action
C
C
1
0
0 003 pF R
3 0 pF
S
Clears interrupt timer
chain
Clears interrupt output
logic
Clears test mode
Stops clock running
Load real-time into device
time registers minutes to
leap years
Starts timekeeping
synchronized to an
external time source
Commence interrupt
timing if so required
Selects test mode
Starts clock timing
‘‘Data Changed’’ signal is
read
16 384 kHz appears on
DB0
35 k
Result
Result
TL F 6681 – 5