ATTINY24A-SSU Atmel, ATTINY24A-SSU Datasheet - Page 31

• Manufacturer Part Number: ATTINY24A-SSU
• Description: MCU AVR 2K FLASH 20MHZ 14SOIC
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY24A-SSU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 12
• Program Memory Size: 2KB (1K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 128 x 8
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Processor Series: ATTINY2x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 128 B
• Interface Type: SPI, USI
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 12
• Number Of Timers: 2
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 20 Channel
• For Use With: ATSTK505 - ADAPTER KIT FOR 14PIN AVR MCU
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.5
6.5.1
6.5.2
8183C–AVR–03/11
Register Description
OSCCAL – Oscillator Calibration Register
CLKPR – Clock Prescale Register
• Bits 7:0 – CAL[7:0]: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to
remove process variations from the oscillator frequency. A pre-programmed calibration value is
automatically written to this register during chip reset, giving the Factory calibrated frequency as
specified in
the oscillator frequency. The oscillator can be calibrated to frequencies as specified in
2 on page
Note that this oscillator is used to time EEPROM and Flash write accesses, and these write
times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to more
than 8.8 MHz. Otherwise, the EEPROM or Flash write may fail.
The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives the
lowest frequency range, setting this bit to 1 gives the highest frequency range. The two fre-
quency ranges are overlapping, in other words a setting of OSCCAL = 0x7F gives a higher
frequency than OSCCAL = 0x80.
The CAL[6:0] 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. See
ical frequencies.
To ensure stable operation of the MCU the calibration value should be changed in small. A vari-
ation in frequency of more than 2% from one cycle to the next can lead to unpredicatble
behavior. Changes in OSCCAL should not exceed 0x20 for each calibration. It is required to
ensure that the MCU is kept in Reset during such changes in the clock frequency.
• Bit 7 – CLKPCE: Clock Prescaler Change Enable
The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. The CLKPCE
bit is only updated when the other bits in CLKPR are simultaniosly written to zero. CLKPCE is
cleared by hardware four cycles after it is written or when the CLKPS bits are written. 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 in the ATtiny24A/44A/84A and will always read as zero.
Bit
0x31 (0x51)
Read/Write
Initial Value
Bit
0x26 (0x46)
Read/Write
Initial Value
175. Calibration outside that range is not guaranteed.
“Calibrated 8 MHz RC Oscillator Frequency vs. OSCCAL Value” on page 238
Table 20-2 on page
CLKPCE
CAL7
R/W
R/W
7
7
0
CAL6
R/W
6
R
6
–
0
175. The application software can write this register to change
Device Specific Calibration Value
CAL5
R/W
5
R
5
–
0
CAL4
R/W
4
4
R
0
–
CLKPS3
CAL3
R/W
R/W
3
3
ATtiny24A/44A/84A
CLKPS2
CAL2
See Bit Description
R/W
R/W
2
2
CLKPS1
CAL1
R/W
R/W
1
1
CLKPS0
CAL0
R/W
R/W
0
0
Table 20-
OSCCAL
CLKPR
for typ-
31