PIC18F27J53T-I/SO Microchip Technology, PIC18F27J53T-I/SO Datasheet - Page 252

• Manufacturer Part Number: PIC18F27J53T-I/SO
• Description: 28-pin, USB, 128KB Flash, 4KB RAM, 12 MIPS, 12-bit ADC, NanoWatt XLP 28 SOIC .30
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F27J53T-I/SO

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 48MHz
• Connectivity: I²C, LIN, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2.15 V ~ 3.6 V
• Data Converters: A/D 10x10b/12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 3.8 KB
• Interface Type: I2C, SPI, USART
• Maximum Clock Frequency: 48 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 8
• Operating Supply Voltage: 2.15 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

PIC18F47J53 FAMILY
TABLE 17-3:
The Alarm Value register window (ALRMVALH and
ALRMVALL) uses the ALRMPTR bits (ALRMCFG<1:0>)
to select the desired Alarm register pair.
By reading or writing to the ALRMVALH register, the
Alarm Pointer value, ALRMPTR<1:0>, decrements
by 1 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 17-4:
17.2.9
The real-time crystal input can be calibrated using the
periodic auto-adjust feature. When properly calibrated,
the RTCC can provide an error of less than three
seconds per month.
To perform this calibration, find the number of error
clock pulses and store the value in the lower half of the
RTCCAL register. The 8-bit, signed value, loaded into
RTCCAL, is multiplied by four and will either be added
or subtracted from the RTCC timer, once every minute.
DS39964B-page 252
ALRMPTR<1:0>
RTCPTR<1:0>
00
01
10
11
00
01
10
11
CALIBRATION
RTCVALH AND RTCVALL
REGISTER MAPPING
ALRMVAL REGISTER
MAPPING
ALRMVAL<15:8> ALRMVAL<7:0>
RTCVAL<15:8>
RTCC Value Register Window
Alarm Value Register Window
ALRMMNTH
WEEKDAY
MINUTES
ALRMMIN
ALRMWD
MONTH
—
—
RTCVAL<7:0>
SECONDS
ALRMSEC
ALRMDAY
ALRMHR
HOURS
YEAR
DAY
—
Preliminary
To calibrate the RTCC module:
1.
2.
EQUATION 17-1:
3.
Writes to the RTCCAL register should occur only when
the timer is turned off, or immediately after the rising
edge of the seconds pulse.
Note:
(Ideal Frequency (32,768) – Measured Frequency) *
60 = Error Clocks per Minute
Use another timer resource on the device to find
the error of the 32.768 kHz crystal.
Convert the number of error clock pulses per
minute (see Equation 17-1).
• If the oscillator is faster than ideal (negative
• If the oscillator is slower than ideal (positive
Load the RTCCAL register with the correct
value.
result from step 2), the RTCCFG register value
needs to be negative. This causes the specified
number of clock pulses to be subtracted from
the timer counter, once every minute.
result from step 2), the RTCCFG register value
needs to be positive. This causes the specified
number of clock pulses to be added to the timer
counter, once every minute.
In determining the crystal’s error value, it
is the user’s responsibility to include the
crystal’s initial error from drift due to
temperature or crystal aging.
CONVERTING ERROR
CLOCK PULSES
 2010 Microchip Technology Inc.