4 adc clock register, Adc clock register – Freescale Semiconductor MC68HC908MR32 User Manual

Page 55

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I/O Registers

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

Freescale Semiconductor

55

In 8-bit mode, this 8-bit result register holds the eight MSBs of the 10-bit result. This register is updated
each time an ADC conversion completes. In 8-bit mode, this register contains no interlocking with ADRH.

3.7.4 ADC Clock Register

This register selects the clock frequency for the ADC, selecting between modes of operation.

ADIV2:ADIV0 — ADC Clock Prescaler Bits

ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate
the internal ADC clock.

Table 3-2

shows the available clock configurations.

Address:

$0042

Bit 7

6

5

4

3

2

1

Bit 0

Read:

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

Write:

R

R

R

R

R

R

R

R

Reset:

Unaffected by reset

R

= Reserved

Figure 3-8. ADC Data Register Low (ADRL) Right Justified Mode

Address:

$0042

Bit 7

6

5

4

3

2

1

Bit 0

Read:

AD9

AD8

AD7

AD6

AD5

AD4

AD3

AD2

Write:

R

R

R

R

R

R

R

R

Reset:

Unaffected by reset

R

= Reserved

Figure 3-9. ADC Data Register Low (ADRL) 8-Bit Mode

Address:

$0043

Bit 7

6

5

4

3

2

1

Bit 0

Read:

ADIV2

ADIV1

ADIV0

ADICLK

MODE1

MODE0

0

0

Write:

R

Reset:

0

0

0

0

0

1

0

0

R

= Reserved

Figure 3-10. ADC Clock Register (ADCLK)

Table 3-2. ADC Clock Divide Ratio

ADIV2

ADIV1

ADIV0

ADC Clock Rate

0

0

0

ADC input clock

÷ 1

0

0

1

ADC input clock

÷ 2

0

1

0

ADC input clock

÷ 4

0

1

1

ADC input clock

÷ 8

1

X

X

ADC input clock

÷ 16

X = don’t care

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