V3022 Datasheet, PDF (10/15 Pages) EM Microelectronic - MARIN SA – Very Low Power 8-Bit 32 kHz RTC Module with Digital Trimming and High Level Integration

R
Communication Sequence
A/D =0
A/D =1
Fig. 8
Access Considerations
The communication sequence shown in Fig.8 is re-
entrant. When the address is written to the V3022 (ie. first
step of the communication sequence) it is stored in an
internal address latch. Software can read the internal
address latch at any time by holding the /D line low during
a read from the V3022. So, for example, an interrupt
routine can read the address latch and push it on to a
stack, popping it when finished to restore the V3022. N.B.
Alarm and timer interrupt routines can reprogram the
alarm and timer without it being necessary to read or
reprogram the clock.
Commands
The commands allow software to transfer the clock and
timer parameters in a sequence (eg. seconds, minutes,
hours, etc.) without any danger of an internal time update
with carry over corrupting the data. They also avoid
delaying internal time updates while using the V3022, as
updates occurring in the reserved clock and timer area
are invisible to software. Software writes or reads
parameters to or from the RAM only.
There are three commands that occupy the command
address space in the RAM.
The function of these commands is to transfer data from
the reserved clock and timer area to the RAM or to
transfer data in the opposite direction, from the RAM to
the reserved clock and timer area. The commands take
place in two steps as do all other communications. The
command address is sent with A /D low. This is followed
by either a read ( RD ) or a write ( WR ) , with A /D high,
to determine the direction of the transfer. If the second
step is a read then the data is transferred from the
reserved clock and timer area to the RAM and if the
second step is a write then the data that has already been
loaded into the RAM clock and/or timer locations is
transferred to the reserved clock and/or timer area.
V3022
Clock and Calendar
The time and date locations in RAM (see Table 9) provide
access to the 1/100 seconds, seconds, minutes, hours,
date, month, year, week day and week number. These
parameters have the ranges indicated in Table 9. The
V3022 may be programmed for 12 or 24 hour time format
(see section "12/24 Data Format"). If a parameter is found
to be out of range, it will be cleared when the units value
on its being next incremented is equal to or greater than 9
eg. B2 will be set to 00 after the units have incremented to
9 (ie. B9 to 00). The device incorporates leap year
correction and week number calculation at the beginning
of a year. If the first day of the year is day 05, 06 or 07 of
the week, then it is given a zero week number, otherwise
it becomes week 1. Week days are numbered from 1 to 7
with Monday as day 1.
Reading of the current time and date must be preceded
by a clock command. The time and date from the last
clock command is held unchanged in RAM.
When transferring data to the reserved clock and timer
area remember to clear the time set lock bit first.
Timer
The timer can be used either for counting elapsed time, or
for giving an interrupt ( IRQ ) on being incremented from
23:59:59:99 to 00:00:00:00. The timer counts up with a
resolution of 1/100 second in the timer reserved areas.
The timer enable/disable bit (addr. 00 hex, bit 3) must be
set by software to allow the timer to be incremented. The
timer is incremented in the reserved timer area, every
internal time update (10 ms). The timer flag (addr. 01
hex, bit 6) is set when the timer rolls over from
23:59:59:99 to 00:00:00:00 and the IRQ becomes active
if the timer mask bit (addr. 01, bit 2) is set. The IRQ will
remain active until software acknowledges the interrupt by
clearing the timer flag. The timer is incremented in the
standby mode, however it will not cause IRQ to become
active until power (VDD) has been restored.
Note: The user should ensure that a time lapse of at least
60 microseconds exists between the falling edge of the
IRQ and the clearing of the timer flag.
Copyright © 2004, EM Microelectronic-Marin SA
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