B.1.14 Quadrature Decoder Improvements

The quadrature decoder counters can now be expanded to 10 bits instead of 8 bits. This is controlled by bit 5 in QDCR, listed in Table B-28.The additional two bits can be read in the QDCxHR registers, listed in Table B-29.

NOTE: Bit 5 of QDCR was always written with a zero in the original Rabbit 3000 chip.

Table B-28. Quadrature Decoder Control Register

Quadrature Decoder Control Register

(QDCR)

(Address = 0x0091)

 

 

 

 

 

Bit(s)

Value

 

Description

 

 

 

 

7:6

00

Disable Quadrature Decoder 2 inputs. Writing a new value to these bits will not

cause Quadrature Decoder 2 to increment or decrement.

 

 

 

 

 

 

01

This bit combination is reserved and should not be used.

 

 

 

 

 

10

Quadrature Decoder 2 inputs from Port F bits 3 and 2.

 

 

 

 

 

 

11

Quadrature Decoder 2 inputs from Port F bits 7 and 6.

 

 

 

 

 

5

0

Eight bit quadrature decoder counters.

 

 

 

 

 

 

1

Ten bit quadrature decoder counters.

 

 

 

 

 

4

 

This bit is reserved and should be written as zero.

 

 

 

 

3:2

00

Disable Quadrature Decoder 1 inputs. Writing a new value to these bits will not

cause Quadrature Decoder 1 to increment or decrement.

 

 

 

 

 

 

01

This bit combination is reserved and should not be used.

 

 

 

 

 

10

Quadrature Decoder 1 inputs from Port F bits 1 and 0.

 

 

 

 

 

 

11

Quadrature Decoder 1 inputs from Port F bits 5 and 4.

 

 

 

 

 

1:0

00

Quadrature Decoder interrupts are disabled.

 

 

 

 

 

 

01

Quadrature Decoder interrupt use Interrupt Priority 1.

 

 

 

 

 

 

10

Quadrature Decoder interrupt use Interrupt Priority 2.

 

 

 

 

 

 

11

Quadrature Decoder interrupt use Interrupt Priority 3.

 

 

 

 

 

 

Table B-29. Quadrature Decoder Count High Register

Quadrature Decoder Count High Register

(QDC1HR)

(Address = 0x0095)

 

 

 

(QDC2HR)

(Address = 0x0097)

 

 

 

 

 

Bit(s)

Value

 

Description

 

 

 

 

 

7:2

read

These bits are reserved and will always read as zeros.

 

 

 

 

1:0

read

The current value of bits 9-8 of the Quadrature Decoder counter is reported.

 

 

 

 

 

314

Rabbit 3000 Microprocessor

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Image 323
Jameco Electronics 2000 Quadrature Decoder Improvements, Table B-28. Quadrature Decoder Control Register, QDC1HR, QDC2HR