The TDS9092 keeps date and time as standard, even in the low power 3mA mode. You can keep these even with the card switched off, in any of three ways:
q SMARTWATCH: a socket which plugs into
the TDS9092 application position, and the final PROM goes into this. The type
number is Dallas Semiconductor DS1216E. You read and write the date and time
by means of W@
which you'll find in the TDS9092 library software routine _SMART.TDS. Usually
you use W@
to set the board clock in the power-up initialisation and when you want the
time read it from there (see TIMEKEEPING).
Occasionally, for instance once a day, you may update the board clock by re-using
PCF8573P: This is a
16-lead dual-in-line clock device which can be connected to the TDS9092 by just
the two-wire I2C bus and +5V power supply. It is made non-volatile
by adding a back-up battery. A particular feature of this chip is an output
which becomes valid when the clock matches a pre-set alarm time. This can used
to switch on a TDS9092 at regular intervals, with only the clock chip current
of 10�A in between. The chip also provides square waves with 1 second and 1
minute periods. Software support is in file _PCF8573.TDS.
q PCF8583FP: This is an 8-lead clock device available in surface mount and is the clock used on the TDS2020F, the TDS9092's more powerful cousin. It can be connected to the TDS9092 by just the two-wire I2C bus and +5V power supply. Features are similar to PCF8573P but it lacks second and minute outputs. Software support is in file _PCF8583.TDS .