ATMEGA128RFR2_14 Datasheet, PDF (131/611 Pages) ATMEL Corporation – Microcontroller with Low Power

ATmega256/128/64RFR2
Register Bits
Value
0xE
0xF
Description
3.600V / 2.40V (BATMON_HR=1/0)
3.675V / 2.45V (BATMON_HR=1/0)
9.12.25 XOSC_CTRL – Crystal Oscillator Control Register
Bit
7
6
NA ($152)
Read/Write
Initial Value
Bit
XTAL_MODE3
RW
1
3
XTAL_MODE2
RW
1
2
NA ($152)
Read/Write
Initial Value
XTAL_TRIM3
RW
0
XTAL_TRIM2
RW
0
5
XTAL_MODE1
RW
1
1
XTAL_TRIM1
RW
0
4
XTAL_MODE0
RW
1
0
XTAL_TRIM0
RW
0
XOSC_CTRL
XOSC_CTRL
This register controls the operation of the 16MHz crystal oscillator.
• Bit 7:4 – XTAL_MODE3:0 - Crystal Oscillator Operating Mode
These register bits set the operating mode of the 16 MHz crystal oscillator. For normal
operation the default value is set to XTAL_MODE = 0xF after reset. For use with an
external clock source it is recommended to set XTAL_MODE = 0x4.
Table 9-65 XTAL_MODE Register Bits
Register Bits
Value
Description
XTAL_MODE3:0
0x4
Internal crystal oscillator disabled; use
external reference frequency.
0xF
Internal crystal oscillator enabled; amplitude
regulation of oscillation enabled.
• Bit 3:0 – XTAL_TRIM3:0 - Crystal Oscillator Load Capacitance Trimming
These register bits control two internal capacitance arrays connected to pins XTAL1
and XTAL2. A capacitance value in the range from 0 pF to 4.5 pF is selectable with a
resolution of 0.3 pF.
Table 9-66 XTAL_TRIM Register Bits
Register Bits
Value
Description
XTAL_TRIM3:0
0x0
0.0 pF, trimming capacitors disconnected
0x1
0.3 pF, trimming capacitor switched on
0x2
...
0xF
4.5 pF, trimming capacitor switched on
9.12.26 RX_SYN – Transceiver Receiver Sensitivity Control Register
Bit
7
NA ($155)
Read/Write
Initial Value
RX_PDT_DIS
RW
0
6
RX_OVERRIDE
RW
1
RX_SYN
8393C-MCU Wireless-09/14
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