MC68HC05L28 Datasheet, PDF (29/156 Pages) Motorola, Inc – Flexible general-purpose microcomputer

2.2.5 OSC1, OSC2
2
These pins provide control input for an on-chip oscillator circuit. A crystal connected to these pins
supplies the oscillator clock. The oscillator frequency (f_OSC) is divided by two to give the internal
bus frequency (f_OP).
OSC1
MCU
OSC2
R_P
OSC1
L
C₁
R_S
C₀
OSC2
(b) Crystal equivalent circuit
C_OSC1
C_OSC2
(a) Crystal oscillator connections
MCU
OSC1
OSC2
External
NC
Clock
(c) External clock source connections
Crystal
2MHz 4MHz Unit
R_S(max) 400
75
Ω
C₀
5
7
pF
C₁
8
12
nF
C_OSC1 15 – 40 15 – 30 pF
C_OSC2 15 – 30 15 – 25 pF
R_P
10
10 M Ω
Q
30 000 40 000 —
(d) Crystal parameters
Figure 2-3 Oscillator connections
MC68HC05L28 MODES OF OPERATION AND PIN DESCRIPTIONS
TPG
MOTOROLA
2-7