MCMC68HC05L16 Freescale Semiconductor, Inc, MCMC68HC05L16 Datasheet - Page 68

• Manufacturer Part Number: MCMC68HC05L16
• Description: M68hc05 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Oscillators/Clock Distributions
FOSCE — Fast (Main) Oscillator Enable
OPTM — Option Map Select
68
The FOSCE bit controls the main oscillator activity. This bit should not be cleared by the CPU when
the main oscillator is selected as the system clock source.
When this bit is cleared:
When this bit is set:
The OPTM bit selects one of two register maps at $0000–$000F. This bit is cleared on reset.
1.
2.
3.
1.
2.
0 = Main register map selected
1 = Option map selected
OSC is shut down.
7-bit divider at the OSC input and POR counter are initialized to $0078.
FTUP flag is cleared.
Main oscillator starts again.
FTUP flag is set by the POR counter overflow (8072 clocks).
SYS1
0
0
1
1
SYS0
0
1
0
1
Table 7-6. System Bus Clock Frequency Selection
MC68HC05L16 • MC68HC705L16 Data Sheet, Rev. 4.1
Divide Ratio
OSC ÷ 64
XOSC ÷ 2
OSC ÷ 2
OSC ÷ 4
OSC = 4.0 M
62.5 k
2.0 M
1.0 M
—
CPU Bus Frequency (Hz)
OSC = 4.1943 M
2.0972 M
1.0486 M
65.536 k
—
XOSC = 32.768 k
16.384 k
—
—
—
Freescale Semiconductor