Cutler-Hammer D320 PLC, Руководство пользователя

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Chapter 6: Instructions
127
Instruction
Mnemonic Decoder and Encoder with 8421 Range
Bit
■ Word
ENCO
DECO ENCO: 8421 encoder
DECO: 8421 decoder
Double words
Ladder
ENCO: Inspect the S register. If there is a bit in the On state, encode
it (on bit n) and store it in the low-order 8 bits of D. If there are two
or more bits in the S register that are in the On state, only the highest
bit will be processed. The higher 8 bits of D do not change.
DECO: Interpret the lower 4 bits of the S register and store in D.
Description
1. ENCO: Set D to the value of the bit number of highest bit in S that is On (0 to 16). If there are
two or more On bits in S, use the location of the highest bit. The high-order 8 bits of D do not
change.
2. DECO: Set the bit location (0 to 15) in D pointed to by the value in the low 4 bits of S. All
other bits in D are reset to 0.
ENCO $0000
→
$00 $0020
→
$06 $0800
→
$0C
$0001 → $01 $0040 → $07 $1000 → $0D
$0002
→
$02 $0080
→
$08 $2000
→
$0E
$0004
→
$03 $0100
→
$09 $4000
→
$0F
$0008 → $04 $0200 → $0A $8000 → $10
$0010
→
$05 $0400
→
$0B
DECO $0
→
$0001 $6
→
$0040 $C
→
$1000
$1
→
$0002 $7
→
$0080 $D
→
$2000
$2
→
$0004 $8
→
$0100 $E
→
$4000
$3
→
$0008 $9
→
$0200 $F
→
$8000
$4
→
$0010 $A
→
$0400
$5
→
$0020 $B
→
$0800
ENCO
D =
S =
R
R
DECO
D =
S =
15..8 7 6 5 4 3 2 1 0
S 0..0 0 1 1 1 0 0 0 0
D 0 0 0 0 0 1 1 1 6+1=7
invar
iable
ENCO
S ..... x x x x 0 1 0 1 = 5
D 0..0 0 0 1 0 0 0 0 0
15..8 7 6 5 4 3 2 1 0
DECO