PIC24FJ128GA Datasheet, PDF (152/232 Pages) Microchip Technology – General Purpose, 16-Bit Flash Microcontrollers

PIC24FJ128GA FAMILY
18.1 RTCC Module Registers
The RTCC module registers are organized into three
categories:
• RTCC Control Registers
• RTCC Value Registers
• Alarm Value Registers
18.1.1 REGISTER MAPPING
To limit the register interface, the RTCC Timer and
Alarm Time registers are accessed through corre-
sponding register pointers. The RTCC Value register
window (RTCVALH and RTCVALL) uses the RTCPTR
bits (RCFGCAL<9:8>) to select the desired timer
register pair (see Table 18-1).
By writing the RTCVALH byte, the RTCC pointer value
RTCPTR<1:0> decrements by one until it reaches ‘00’.
Once it reaches ‘00’, the MINUTES and SECONDS
value will be accessible through RTCVALH and
RTCVALL until the pointer value is manually changed.
TABLE 18-1:
RTCPTR
<1:0>
00
01
10
11
RTCVAL REGISTER MAPPING
RTCC Value Register Window
RTCVAL<15:8> RTCVAL<7:0>
MINUTES
WEEKDAY
MONTH
—
SECONDS
HOURS
DAY
YEAR
The Alarm Value register window (ALRMVALH and
ALRMVALL) uses the ALRMPTR bits
(ALCFGRPT<9:8>) to select the desired alarm register
pair (see Table 18-2).
By writing the ALRMVALH byte, the alarm pointer value
ALRMPTR<1:0> decrements by one until it reaches
‘00’. Once it reaches ‘00’, the ALRMMIN and
ALRMSEC value will be accessible through
ALRMVALH and ALRMVALL until the pointer value is
manually changed.
TABLE 18-2: ALRMVAL REGISTER
MAPPING
ALRMPTR
Alarm Value Register Window
<1:0>
ALRMVAL<15:8> ALRMVAL<7:0>
00
ALRMMIN
ALRMSEC
01
ALRMWD
ALRMHR
10
ALRMMNTH
ALRMDAY
11
—
—
Considering that the 16-bit core does not distinguish
between 8-bit and 16-bit read operations, the user must
be aware that when reading either the ALRMVALH or
ALRMVALL bytes will decrement the ALRMPTR<1:0>
value. The same applies to the RTCVALH or RTCVALL
bytes with the RTCPTR<1:0> being decremented.
Note: This only applies to read operations and
not write operations.
DS39747C-page 150
Preliminary
© 2006 Microchip Technology Inc.