MC68HC908RF2CFA Freescale Semiconductor, MC68HC908RF2CFA Datasheet - Page 68

• Manufacturer Part Number: MC68HC908RF2CFA
• Description: IC MCU W/UHF TX 2K FLASH 32LQFP
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC68HC908RF2CFA

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 4MHz
• Peripherals: LVD, POR, PWM, RF Mod
• Number Of I /o: 12
• Program Memory Size: 2KB (2K x 8)
• Program Memory Type: FLASH
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 3.6 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -
• Connectivity: -

Internal Clock Generator Module (ICG)
6.3.2.1 Digitally Controlled Oscillator
6.3.2.2 Modulo N Divider
6.3.2.3 Frequency Comparator
Data Sheet
68
The internal clock generator contains:
The digitally controlled oscillator (DCO) is an inaccurate oscillator which generates
the internal clock (ICLK). The clock period of ICLK is dependent on the digital loop
filter outputs (DSTG[7:0] and DDIV[3:0]). Because there is only a limited number of
bits in DDIV and DSTG, the precision of the output (ICLK) is restricted to a
long-term precision of approximately ±0.202 percent to ±0.368 percent when
measured over several cycles (of the desired frequency). Additionally, since the
propagation delays of the devices used in the DCO ring oscillator are a measurable
fraction of the bus clock period, reaching the long-term precision may require
alternately running faster and slower than desired, making the worst case
cycle-to-cycle frequency variation ±6.45 percent to ±11.8 percent (of the desired
frequency). The valid values of DDIV:DSTG range from $000 to $9FF. For more
information on the quantization error in the DCO, see
DCO
The modulo N divider creates the low-frequency base clock (IBASE) by dividing the
internal clock (ICLK) by the ICG multiplier factor (N) contained in the ICG multiplier
register (ICGMR). When N is programmed to a $01 or $00, the divider is disabled
and ICLK is passed through to IBASE undivided. When the internal clock generator
is stable, the frequency of IBASE will be equal to the nominal frequency (f
307.2 kHz ±25 percent.
The frequency comparator effectively compares the low-frequency base clock
(IBASE) to a nominal frequency, f
IBASE to a voltage by charging a known capacitor with a current reference for a
period dependent on IBASE. This voltage is compared to a voltage reference with
comparators, whose outputs are fed to the digital loop filter. The dependence of
these outputs on the capacitor size, current reference, and voltage reference
causes up to ±25 percent error in f
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Output.
A digitally controlled oscillator
A modulo N divider
A frequency comparator, which contains voltage and current references, a
frequency to voltage converter, and comparators
A digital loop filter
Freescale Semiconductor, Inc.
For More Information On This Product,
Internal Clock Generator Module (ICG)
Go to: www.freescale.com
NOM
NOM
. First, the frequency comparator converts
.
6.4.4 Quantization Error in
MC68HC908RF2 — Rev. 4.0
MOTOROLA
NOM
) of