Rainbow-electronics AT77C102B Manual de usuario descargar pdf (Pagina 13)

5364A–BIOM–09/05

AT77C102B

3.10 Synchronization: The Dummy Column

A dummy column has been added to the sensor to act as a specific pattern to detect the first

pixel. Therefore, 280 true columns plus one dummy column are read for each frame.

The four bytes of the dummy column contain a fixed pattern on the first two bytes, and tempera-

ture information on the last two bytes.

Note: x represents 0 or 1

The sequence 111X0000 111X0000 appears on every frame (exactly every 1124 clock pulses),

so it is an easy pattern to recognize for synchronization purposes.

3.11 Thermometer

The dummy bytes DB3 and DB4 contain some internal temperature information.

The even nibble nnnn in DB3 can be used to measure an increase or decrease of the chip’s tem-

perature, using the difference between two measures of the same physical device. The following

table gives values in Kelvin.

Table 1. Dummy Column Description

Dummy Byte Odd Even

Dummy Byte 1 DB1: 111X 0000

Dummy Byte 2 DB2: 111X 0000

Dummy Byte 3 DB3: rrrr nnnn

Dummy Byte 4 DB4: tttt pppp

Table 1. Temperature Table

nnnn

Decimal

nnnn

Binary

Temperature differential with code 8

in Kelvin

15 1111

> 11.2

14 1110

8.4

13 1101

12 1100

5.6

11 1011

4.2

10 1010

2.8

9 1001

1.4

8 1000

7 0111

-1.4

6 0110

-2.8

5 0101

-4.2

4 0100

-5.6

3 0011

-7

2 0010

-8.4

1 0001

-11.2

0 0000

< -16.8

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 19

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Rainbow-electronics AT77C102B Manual de usuario Pagina 13

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