Freescale Semiconductor MCF51QE128RM ICS Control Register 2 ICSC2, ICS Trim Register Icstrm, Bdiv

Models: MCF51QE128RM

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Internal Clock Source (S08ICSV3)

12.3.2ICS Control Register 2 (ICSC2)

R

W

Reset:

7

6

5

4

3

2

1

0

BDIV

 

RANGE

HGO

LP

EREFS

ERCLKEN

EREFSTEN

 

 

 

 

 

 

 

 

0

1

0

0

0

0

0

0

 

 

Figure 12-4. ICS Control Register 2 (ICSC2)

 

 

Table 12-4. ICSC2 Field Descriptions

 

 

 

Field

 

Description

 

 

7:6

Bus Frequency Divider. Selects the amount to divide down the clock source selected by the CLKS bits. This

BDIV

controls the bus frequency.

 

00 Encoding 0 — Divides selected clock by 1

 

01 Encoding 1 — Divides selected clock by 2 (reset default)

 

10 Encoding 2 — Divides selected clock by 4

 

11 Encoding 3 — Divides selected clock by 8

 

 

5

Frequency Range Select. Selects the frequency range for the external oscillator.

RANGE

1

High frequency range selected for the external oscillator

 

0

Low frequency range selected for the external oscillator

 

 

4

High Gain Oscillator Select. The HGO bit controls the external oscillator mode of operation.

HGO

1

Configure external oscillator for high gain operation

 

0

Configure external oscillator for low power operation

 

 

3

Low Power Select. The LP bit controls whether the FLL is disabled in FLL bypassed modes.

LP

1

FLL is disabled in bypass modes unless BDM is active

 

0

FLL is not disabled in bypass mode

 

 

2

External Reference Select. The EREFS bit selects the source for the external reference clock.

EREFS

1

Oscillator requested

 

0

External Clock Source requested

 

 

1

External Reference Enable. The ERCLKEN bit enables the external reference clock for use as ICSERCLK.

ERCLKEN

1

ICSERCLK active

 

0

ICSERCLK inactive

 

 

0

External Reference Stop Enable. The EREFSTEN bit controls whether or not the external reference clock

EREFSTEN

remains enabled when the ICS enters stop mode.

 

1

External reference clock stays enabled in stop if ERCLKEN is set before entering stop

 

0

External reference clock is disabled in stop

 

 

 

12.3.3ICS Trim Register (ICSTRM)

7

6

5

4

3

2

1

0

R

W

Reset:

TRIM

Note: TRIM is loaded during reset from a factory programmed location when not in BDM mode. If in a BDM mode, a default value of 0x80 is loaded.

Figure 12-5. ICS Trim Register (ICSTRM)

MCF51QE128 MCU Series Reference Manual, Rev. 3

Freescale Semiconductor

251

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Freescale Semiconductor MCF51QE128RM ICS Control Register 2 ICSC2, ICS Trim Register Icstrm, ICSC2 Field Descriptions