Chapter 4 - discrete transfers, Discrete writes, Bit shift – Hardy HI 2151/30WC Single-Scale Controller User Manual

Page 17: Weight parameter, Bit shift -1 weight parameter -1, Fig. 5-1 b, Fig. 5-2 b, Chapter 4 - discrete transfers -1

Chapter 4 - Discrete Transfers

4-1

CHAPTER 4 - DISCRETE TRANSFERS

Discrete Writes

The PLC places two sixteen bit words in the Output Image Table which
are read by the HI 2151WC weight controller. The second word defines
which weight data the HI 2151WC should place in the Input Image
Table for the PLC to read. The first word is reserved for future use. Pro-
grams should send all zeros for the first word to avoid conflict with
future revisions of the command set.

Structure of the Two
Words in the PLC
Output Image Table

Bit Shift

A number from 0 to 4 specifies the number of bits to shift the 16 bit
window from the right of the internal 20 bit value. This sixteen bit win-
dow is the weight value that will be placed in the PLC Input Image
Table. See the section on resolution for additional information. Once
the sixteen bit value is read by the PLC, it can be multiplied by the fac-
tor shown below to yield the actual weight value.

0 = No shift, the lowest 16 bits are transferred.
1 = Shift one digit, multiply by 2 to achieve actual weight value
2 = Shift two digits, multiply by 4 to achieve actual weight value
3 = Shift three digits, multiply by 8 to achieve actual weight value
4 = Shift four digits, multiply by 16 to achieve actual weight value

Weight Parameter

Select either Gross weight, Net weight, Rate-of-Change (mass flow),
peak force (or peak weight), or Test weight to be placed in the PLC
Input Image Table.

NOTE:

All weight parameters are in the units (lbs., kgs.) used during calibration.

0 = Gross Weight (Standard)
1 = Net Weight (Standard)
2 = Rate-Of-Change (mass flow) (Optional)
3 = Peak weight or force (Optional)
4 = Test weight (an arbitrary incrementing value)

bits: 15-12

bits: 11-8

bits: 7-4

bits: 3-0

First Word of
the Quarter

reserved for
future use

Second
Word of the
Quarter

bit shift

weight
parameter

1st status
byte

2nd status
byte

TABLE 4-1: DISCRETE WRITE - 2 WORDS (16 BITS EACH)