ATA6616-P3QW Atmel, ATA6616-P3QW Datasheet - Page 62

• Manufacturer Part Number: ATA6616-P3QW
• Description: TXRX MULTICHIP MOD LIN SIP 38QFN
• Manufacturer: Atmel
• Series: AVR® ATA66 LIN-SBCr

Specifications of ATA6616-P3QW

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, LIN, SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 16
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 38-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.5.5.2
62
Atmel ATA6616/ATA6617
CLKPR – Clock Prescaler Register
The CAL6..0 bits are used to tune the frequency within the selected range. A setting of 0x00
gives the lowest frequency in that range, and a setting of 0x7F gives the highest frequency in
the range. Incrementing CAL6..0 by 1 will give a frequency increment of less than 2% in the
frequency range 7.3 - 8.1MHz.
• Bit 7 – CLKPCE: Clock Prescaler Change Enable
The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. The CLK-
PCE bit is only updated when the other bits in CLKPR are simultaneously written to zero.
CLKPCE is cleared by hardware four cycles after it is written or when the CLKPS bits are writ-
ten. Rewriting the CLKPCE bit within this time-out period does neither extend the time-out
period, nor clear the CLKPCE bit.
• Bits 6:4 – Res: Reserved Bits
These bits are reserved bits in the Atmel
• Bits 3:0 – CLKPS3:0: Clock Prescaler Select Bits 3 - 0
These bits define the division factor between the selected clock source and the internal sys-
tem clock. These bits can be written run-time to vary the clock frequency to suit the application
requirements. As the divider divides the master clock input to the MCU, the speed of all syn-
chronous peripherals is reduced when a division factor is used. The division factors are given
in
To avoid unintentional changes of clock frequency, a special write procedure must be followed
to change the CLKPS bits:
Interrupts must be disabled when changing prescaler setting in order not to disturb the
procedure.
The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed,
the CLKPS bits will be reset to “0000”. If CKDIV8 is programmed, CLKPS bits are reset to
“0011”, giving a division factor of eight at start up. This feature should be used if the selected
clock source has a higher frequency than the maximum frequency of the device at the present
operating conditions. Note that any value can be written to the CLKPS bits regardless of the
CKDIV8 Fuse setting. The Application software must ensure that a sufficient division factor is
chosen if the selected clock source has a higher frequency than the maximum frequency of
the device at the present operating conditions. The device is shipped with the CKDIV8 Fuse
programmed.
Bit
Read/Write
Initial Value
1. Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits in
2. Within four cycles, write the desired value to CLKPS while writing a zero to CLKPCE.
Table
CLKPR to zero.
4-14.
CLKPCE
R/W
7
0
R
6
–
0
R
0
5
–
®
ATtiny87/167 and will always read as zero.
R
4
–
0
CLKPS3 CLKPS2 CLKPS1 CLKPS0 CLKPR
R/W
3
See Bit Description
R/W
2
R/W
1
R/W
0
9132D–AUTO–12/10