PIC18F2510-I/ML Microchip Technology Inc., PIC18F2510-I/ML Datasheet - Page 119

• Manufacturer Part Number: PIC18F2510-I/ML
• Description: Microcontroller; 32 KB Flash; 1024 RAM; 0 EEPROM; 21 I/O; 28-Pin-QFN
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F2510-I/ML

• A/d Inputs: 10-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 0 Bytes
• Input Output: 21
• Interface: I2C/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin QFN
• Programmable Memory: 32K Bytes
• Ram Size: 1.5K Bytes
• Speed: 40 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

11.2
Timer1 can be configured for 16-bit reads and writes
(see Figure 11-2). When the RD16 control bit
(T1CON<7>) is set, the address for TMR1H is mapped
to a buffer register for the high byte of Timer1. A read
from TMR1L will load the contents of the high byte of
Timer1 into the Timer1 High Byte Buffer register. This
provides the user with the ability to accurately read all
16 bits of Timer1 without having to determine whether
a read of the high byte, followed by a read of the low
byte, has become invalid due to a rollover between
reads.
A write to the high byte of Timer1 must also take place
through the TMR1H Buffer register. The Timer1 high
byte is updated with the contents of TMR1H when a
write occurs to TMR1L. This allows a user to write all
16 bits to both the high and low bytes of Timer1 at once.
The high byte of Timer1 is not directly readable or
writable in this mode. All reads and writes must take
place through the Timer1 High Byte Buffer register.
Writes to TMR1H do not clear the Timer1 prescaler.
The prescaler is only cleared on writes to TMR1L.
11.3
An on-chip crystal oscillator circuit is incorporated
between pins T1OSI (input) and T1OSO (amplifier
output). It is enabled by setting the Timer1 Oscillator
Enable bit, T1OSCEN (T1CON<3>). The oscillator is a
low-power circuit rated for 32 kHz crystals. It will
continue to run during all power-managed modes. The
circuit for a typical oscillator is shown in Figure 11-3.
Table 11-1 shows the capacitor selection for the Timer1
oscillator.
The user must provide a software time delay to ensure
proper start-up of the Timer1 oscillator.
FIGURE 11-3:
© 2006 Microchip Technology Inc.
Note:
Timer1 16-Bit Read/Write Mode
Timer1 Oscillator
27 pF
27 pF
C1
C2
See the Notes with Table 11-1 for additional
information about capacitor selection.
32.768 kHz
XTAL
EXTERNAL
COMPONENTS FOR THE
TIMER1 OSCILLATOR
T1OSI
T1OSO
PIC18F45J10
Preliminary
PIC18F45J10 FAMILY
TABLE 11-1:
11.3.1
The Timer1 oscillator is also available as a clock source
in power-managed modes. By setting the clock select
bits, SCS1:SCS0 (OSCCON<1:0>), to ‘01’, the device
switches to SEC_RUN mode; both the CPU and
peripherals are clocked from the Timer1 oscillator. If the
IDLEN bit (OSCCON<7>) is cleared and a SLEEP
instruction is executed, the device enters SEC_IDLE
mode. Additional details are available in Section 3.0
“Power-Managed Modes”.
Whenever the Timer1 oscillator is providing the clock
source, the Timer1 system clock status flag, T1RUN
(T1CON<6>), is set. This can be used to determine the
controller’s current clocking mode. It can also indicate
the clock source being currently used by the Fail-Safe
Clock Monitor. If the Clock Monitor is enabled and the
Timer1 oscillator fails while providing the clock, polling
the T1RUN bit will indicate whether the clock is being
provided by the Timer1 oscillator or another source.
Oscillator
Note 1: Microchip suggests these values as a
Type
LP
2: Higher capacitance increases the stability
3: Since each resonator/crystal has its own
4: Capacitor values are for design guidance
USING TIMER1 AS A
CLOCK SOURCE
starting point in validating the oscillator
circuit.
of the oscillator but also increases the
start-up time.
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate
components.
only.
32 kHz
Freq.
CAPACITOR SELECTION FOR
THE TIMER OSCILLATOR
values
27 pF
C1
DS39682B-page 117
(1)
of
27 pF
external
C2
(2,3,4)
(1)