Clock Operation

56F802 Technical Data, Rev. 9

Freescale Semiconductor

23

Due to the inherent frequency tolerances required for SCI communication, changing the factory-trimmed

oscillator frequency is not recommended. If modification of the Boot Flash contents are required, code

must be included which retrieves the optimum trim value (from address $103F in the Data Flash

Information Block) and writes it to the IOSCTL register. Note that the IFREN bit in the Data Flash control

register must be set in order to read the Data Flash Information Block.

Figure 3-7 Typical Relaxation Oscillator Frequency vs. Temperature

Table 3-8 Relaxation Oscillator Characteristics

Characteristic

Symbol

Min

Typ

Max

Unit

1. Over full temperature range.

Δf

—

+2

+5

%

Frequency Drift over Temp

Δf/Δt

—

+0.1

—

Frequency Drift over Supply

Δf/ΔV

—

0.1

—

%/V

8.2

8.0

8.3

8.4

7.9

8.1

7.8

75

55

-40

35

-25

15

-5

85