mc68hc908kx8 Freescale Semiconductor, Inc, mc68hc908kx8 Datasheet - Page 187

• Manufacturer Part Number: mc68hc908kx8
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

17.7 Internal Oscillator Characteristics
17.8 External Oscillator Characteristics
Freescale Semiconductor
Internal oscillator base frequency
Internal oscillator tolerance
Internal oscillator multiplier
External clock option
External crystal options
Crystal load capacitance
Crystal fixed capacitance
Crystal tuning capacitance
Feedback bias resistor
Series resistor
1. V
2. Internal oscillator is selectable through software for a maximum frequency. Actual frequency will be
3.
4. Multiplier must be chosen to limit the maximum bus frequency of 4 MHz for 2.7-V operation and 8 MHz for 4.5-V operation.
1. V
2. Setting EXTCLKEN configuration option enables OSC1 pin for external clock square-wave input.
3. No more than 10% duty cycle deviation from 50%
4. EXTSLOW configuration option configures external oscillator for a slow speed crystal and sets the clock monitor circuits
5. Some modules may require a minimum frequency greater than dc for proper operation. See appropriate table for this
6. MCU speed derates from 32 MHz at V
7. Setting EXTCLKEN and EXTXTALEN configuration options enables OSC1 and OSC2 pins for external crystal option.
8.
9. Consult crystal vendor data sheet, see
10. Not required for high-frequency crystals
With ICG clock disabled
With ICG clock enabled
EXTSLOW = 1
EXTSLOW = 0
EXTSLOW = 1
EXTSLOW = 0
f
multiplier (N) x base frequency.
Bus
of the ICG module to expect an external clock frequency that is higher/lower than the internal oscillator base frequency,
f
information.
f
DD
INTOSC.
Bus
DD
= 5.5 Vdc to 2.7 Vdc, V
= (
= 5.5 to 2.7 Vdc, V
= (
f
INTOSC
f
EXTOSC
(9), (10)
(4)
(4)
(4)
(4)
Characteristic
/ 4) x N when internal clock source selected
Characteristic
(2)
/ 4) when external clock source is selected.
(9)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
,
(7)
(9)
(3)
(9)
,
(9)
(4)
(8)
SS
= 0 Vdc, T
SS
(2), (3)
= 0 Vdc, T
(1)
(1)
A
DD
= –40°C to +125°C, unless otherwise noted
Figure 7-3. External Clock Generator Block
A
= 4.5 Vdc to 16 MHz at V
= –40°C to +125°C, unless otherwise noted
f
Symbol
Symbol
f
f
OSC_TOL
f
EXTOSC
EXTOSC
INTOSC
C
C
C
R
R
N
L
1
2
B
S
DD
= 2.7 Vdc.
307.2 k
230.4
dc
30 k
Min
Min
–25
1 M
60
—
—
—
—
—
1
(5)
Diagram.
Internal Oscillator Characteristics
2 x C
2 x C
307.2
Typ
Typ
10
—
—
—
—
—
—
—
—
—
L
L
32 M
307.2 k
32 M
100 k
Max
Max
384
+25
127
8 M
—
—
—
—
—
(6)
(6)
Unit
Unit
kHz
MΩ
MΩ
Hz
Hz
pF
pF
pF
—
%
187