RTC Programming Model
18-10
ADSP-BF537 Blackfin Processor Hardware Reference
When the system wakes up from deep sleep state, software does not need
to W1C the bits in
RTC_ISTAT
. All W1C bits are already cleared by hard-
ware. The seconds event flag is set when the RTC internal V
dd
logic has
completed its restart sequence. Software should wait until the seconds
event flag is set and then may begin reading or writing any RTC register.
Event Flags
a
The unknown values in the registers at powerup can cause event
flags to set before the correct value is written into each of the regis-
ters. By catching the 1 Hz clock edge, the write to
RTC_STAT
can
occur a full second before the write to
RTC_ALARM
. This would cause
an extra second of delay between the validity of
RTC_STAT
and
RTC_ALARM
, if the value of the
RTC_ALARM
out of reset is the same as
the value written to
RTC_STAT
. Wait for the writes to complete on
these registers before using the flags and interrupts associated with
their values.
The following is a list of flags along with the conditions under which they
are valid:
• Seconds (1 Hz) event flag
Always set on the positive edge of the 1 Hz clock and after shadow
registers have updated after waking from deep sleep. This is valid as
long as the RTC 1 Hz clock is running. Use this flag or interrupt to
validate the other flags.
• Write complete and write pending status
Always valid.
• Minutes event flag
Valid only after the second field in
RTC_STAT
is valid. Use the write
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...