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Analog Comparator (S08ACMPV2)

MC9S08JM60 Series Data Sheet, Rev. 5

124

Preliminary

Freescale Semiconductor

8.4

Functional Description

The analog comparator can be used to compare two analog input voltages applied to ACMP+ and ACMP–;

or it can be used to compare an analog input voltage applied to ACMP– with an internal bandgap reference

voltage. ACBGS is used to select between the bandgap reference voltage or the ACMP+ pin as the input

to the non-inverting input of the analog comparator. The comparator output is high when the non-inverting

input is greater than the inverting input, and is low when the non-inverting input is less than the inverting

input. ACMOD is used to select the condition which will cause ACF to be set. ACF can be set on a rising

edge of the comparator output, a falling edge of the comparator output, or either a rising or a falling edge

(toggle). The comparator output can be read directly through ACO. The comparator output can be driven

onto the ACMPO pin using ACOPE.

ACOPE

Analog Comparator Output Pin Enable — ACOPE is used to enable the comparator output to be placed onto

the external pin, ACMPO.

0 Analog comparator output not available on ACMPO

1 Analog comparator output is driven out on ACMPO

1:0

ACMOD

Analog Comparator Mode — ACMOD selects the type of compare event which sets ACF.

00 Encoding 0 — Comparator output falling edge

01 Encoding 1 — Comparator output rising edge

10 Encoding 2 — Comparator output falling edge

11 Encoding 3 — Comparator output rising or falling edge

Table 8-2. ACMP Status and Control Register Field Descriptions (continued)

Field

Description

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