Rockwell-automation 1771-QB Linear Pos. Manual de usuario descargar pdf (Pagina 218)

Appendix

H1

Data Formats

Bit 3 in the parameter control word (word 1 in the parameter block) determines

the format of the data contained in block transfer reads and writes. BCD format

provides compatibility with older programmable controllers. Binary format

provides compatibility with the PLC-5, which uses integer (16-bit 2’s

complement) data. This appendix explains both these numbering formats.

BCD (Binary Coded Decimal) is a numbering format by which decimal digits

are directly represented by 4-bit groups of binary numbers. Here’s how the

decimal digits 0 to 9 are represented:

Table H.A

Binary

Representation

Decimal Digit Binary Representation

0 0000

1 0001

2 0010

3 0011

4 0100

5 0101

60110

70111

8 1000

9 1001

Example: To represent the number 8761 (decimal) using BCD notation, set the

16 bits of the word like this:

1000 0111 0110 0001

8761

Important: In BCD format, none of the four-bit groupings may contain a value

greater than 1001 (binary).

To complement a number means to change it to a negative number. 2’s

complement binary is a method used to represent signed integers in binary

notation. This method is used with PLC-3 and PLC-5 processors.

BCD

2's Complement Binary

1 2 ... 213 214 215 216 217 218 219 220 221 222 223 224 225 226

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Rockwell-automation 1771-QB Linear Pos. Manual de usuario Pagina 218