M48T129 ST Microelectronics, M48T129 Datasheet - Page 14

• Manufacturer Part Number: M48T129
• Description: 3.3V-5V 1 Mbit 128Kb x8 TIMEKEEPER SRAM
• Manufacturer: ST Microelectronics

M48T129Y, M48T129V
Figure 12. Alarm Interrupt Reset Waveform
Figure 13. Back-up Mode Alarm Waveforms
Calibration values, including the number of sec-
onds lost or gained in a given period, can be found
in Application Note: TIMEKEEPER CALIBRA-
TION. This allows the designer to give the end
user the ability to calibrate the clock as the envi-
ronment requires, even if the final product is pack-
aged in a non-user serviceable enclosure. The
designer could provide a simple utility that access-
es the Calibration byte.
The second approach is better suited to a manu-
facturing environment, and involves the use of the
IRQ/FT pin. The pin will toggle at 512Hz, when the
Stop bit (ST, D7 of 1FFF9h) is ’0’,the Frequency
Test bit (FT, D6 of 1FFFCh) is ’1’, the Alarm Flag
14/22
V CC
V PFD (max)
V PFD (min)
V SO
AFE bit in Interrupt Register
AF bit in Flags Register
IRQ/FT
AD0-AD7
ACTIVE FLAG BIT
IRQ/FT
HIGH-Z
ADDRESS 1FF0h
15ns Min
Enable bit (AFE, D7 of 1FFF6h) is ’0’, and the
Watchdog Steering bit (WDS, D7 of 1FFF7h) is ’1’
or the Watchdog Register (1FFF7h=0) is reset.
Note: A 4 second settling time must be allowed
before reading the 512Hz output.
Any deviation from 512Hz indicates the degree
and direction of oscillator frequency shift at the test
temperature.
512.010124Hz would indicate a +20 ppm oscillator
frequency error, requiring a –10 (WR001010) to be
loaded into the Calibration Byte for correction.
Note that setting or changing the Calibration Byte
does not affect the Frequency test output frequen-
cy.
tREC
For
example,
HIGH-Z
AI02581
a
HIGH-Z
AI01678C
reading
of