MC68HC908GP16CFB Freescale Semiconductor, MC68HC908GP16CFB Datasheet - Page 83

• Manufacturer Part Number: MC68HC908GP16CFB
• Description: MCU 8-BIT 16K FLASH 44-QFP
• Manufacturer: Freescale Semiconductor
• Series: HC08r

Specifications of MC68HC908GP16CFB

• Core Processor: HC08
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: SCI, SPI
• Peripherals: LVD, POR, PWM
• Number Of I /o: 33
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-QFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

8.3.3.1 External Oscillator Amplifier
The external oscillator amplifier provides the gain required by an external crystal connected in a Pierce
oscillator configuration. The amount of this gain is controlled by the slow external (EXTSLOW) bit in the
CONFIG. When EXTSLOW is set, the amplifier gain is reduced for operating low-frequency crystals (32
kHz to 100 kHz). When EXTSLOW is clear, the amplifier gain will be sufficient for 1-MHz to 8-MHz
crystals. EXTSLOW must be configured correctly for the given crystal or the circuit may not operate.
The amplifier is enabled when the external clock generator enable (ECGEN) signal is set and when the
external crystal enable (EXTXTALEN) bit in the CONFIG is set. ECGEN is controlled by the clock enable
circuit (see
enabled, the amplifier will be connected between the PTC4/OSC1 and PTC3/OSC2 pins. Otherwise, the
PTC3/OSC2 pin reverts to its port function.
In its typical configuration, the external oscillator requires five external components:
Freescale Semiconductor
1. Crystal, X
2. Fixed capacitor, C
3. Tuning capacitor, C
4. Feedback resistor, RB
5. Series resistor, R
be required for all ranges of operation, especially with high frequency crystals. Refer to the crystal
manufacturer’s data for more information.)
8.3.1 Clock Enable
1
EXTXTALEN
EXTSLOW
NAME
NAME
ECGEN
NAME
NAME
INTERNAL TO MCU
EXTERNAL
S
Figure 8-4. External Clock Generator Block Diagram
1
(included in
2
MODULE SIGNAL
REGISTER BIT
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
(can also be a fixed capacitor)
CONFIGURATION BIT
TOP LEVEL SIGNAL
Circuit) and indicates that the external clock function is desired. When
GENERATOR
EXTERNAL
CLOCK
Figure 8-4
to follow strict Pierce oscillator guidelines and may not
OSC1
PTC4
C
1
R
X
B
1
C
R
These components are required
for external crystal use only.
AMPLIFIER
2
S
*
INPUT PATH
OSC2
PTC3
*R
when used with higher-
frequency crystals. Refer
to manufacturer’s data.
S
can be 0 (shorted)
Functional Description
ECLK
83