MC68908GZ8MFAE Freescale Semiconductor, MC68908GZ8MFAE Datasheet - Page 61

IC MCU 8BIT 8K FLASH 48-LQFP

MC68908GZ8MFAE

Manufacturer Part Number
MC68908GZ8MFAE
Description
IC MCU 8BIT 8K FLASH 48-LQFP
Manufacturer
Freescale Semiconductor
Series
HC08r
Datasheet

Specifications of MC68908GZ8MFAE

Core Processor
HC08
Core Size
8-Bit
Speed
8MHz
Connectivity
CAN, LIN, SCI, SPI
Peripherals
LVD, POR, PWM
Number Of I /o
37
Program Memory Size
8KB (8K x 8)
Program Memory Type
FLASH
Ram Size
1K x 8
Voltage - Supply (vcc/vdd)
3 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 125°C
Package / Case
48-LQFP
Processor Series
M689xx
Core
HC08
Data Bus Width
8 bit
Data Ram Size
1 KB
Interface Type
SPI, SCI, CAN
Maximum Clock Frequency
8 MHz
Number Of Programmable I/os
37
Number Of Timers
2
Operating Supply Voltage
5.5 V
Maximum Operating Temperature
+ 125 C
Mounting Style
SMD/SMT
Development Tools By Supplier
FSICEBASE, M68CBL05AE, DEMO908GZ60E, M68EML08GZE
Minimum Operating Temperature
- 40 C
On-chip Adc
10 bit, 16 Channel
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
Lead Free Status / Rohs Status
 Details
4.3.1 Crystal Oscillator Circuit
The crystal oscillator circuit consists of an inverting amplifier and an external crystal. The OSC1 pin is the
input to the amplifier and the OSC2 pin is the output. The SIMOSCEN signal from the system integration
module (SIM) or the OSCSTOPENB bit in the CONFIG register enable the crystal oscillator circuit.
The CGMXCLK signal is the output of the crystal oscillator circuit and runs at a rate equal to the crystal
frequency. CGMXCLK is then buffered to produce CGMRCLK, the PLL reference clock.
CGMXCLK can be used by other modules which require precise timing for operation. The duty cycle of
CGMXCLK is not guaranteed to be 50% and depends on external factors, including the crystal and related
external components. An externally generated clock also can feed the OSC1 pin of the crystal oscillator
circuit. Connect the external clock to the OSC1 pin and let the OSC2 pin float.
4.3.2 Phase-Locked Loop Circuit (PLL)
The PLL is a frequency generator that can operate in either acquisition mode or tracking mode, depending
on the accuracy of the output frequency. The PLL can change between acquisition and tracking modes
either automatically or manually.
4.3.3 PLL Circuits
The PLL consists of these circuits:
The operating range of the VCO is programmable for a wide range of frequencies and for maximum
immunity to external noise, including supply and CGMXFC noise. The VCO frequency is bound to a range
from roughly one-half to twice the center-of-range frequency, f
CGMXFC pin changes the frequency within this range. By design, f
center-of-range frequency, f
(L × 2
CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency,
f
programmable modulo divider. The modulo divider reduces the VCO clock by a factor, N. The dividers
output is the VCO feedback clock, CGMVDV, running at a frequency, f
information, see
The phase detector then compares the VCO feedback clock, CGMVDV, with the final reference clock,
CGMRDV. A correction pulse is generated based on the phase difference between the two signals. The
loop filter then slightly alters the DC voltage on the external capacitor connected to CGMXFC based on
the width and direction of the correction pulse. The filter can make fast or slow corrections depending on
its mode, described in
reference frequency determines the speed of the corrections and the stability of the PLL.
The lock detector compares the frequencies of the VCO feedback clock, CGMVDV, and the reference
clock, CGMRCLK. Therefore, the speed of the lock detector is directly proportional to the reference
Freescale Semiconductor
RCLK
. The VCO’s output clock, CGMVCLK, running at a frequency, f
E
Voltage-controlled oscillator (VCO)
Modulo VCO frequency divider
Phase detector
Loop filter
Lock detector
)f
NOM
.
4.3.6 Programming the
4.3.4 Acquisition and Tracking
NOM
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 4
, (71.4 kHz) times a linear factor, L, and a power-of-two factor, E, or
PLL.
Modes. The value of the external capacitor and the
VRS
. Modulating the voltage on the
VRS
VCLK
VDV
is equal to the nominal
, is fed back through a
= f
VCLK
/(N). For more
Functional Description
61

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