FP_DECODE

Decode hexadecimal -> bit state

This FP instruction decodes the contents of data specified by s1_Start according to the contents of s2_Control if the trigger EN is set to TRUE. The decoded result is stored in the area starting from d_Start.

FP_DECODE is the inverse instruction of FP_ENCODE.

Parameters

Input

s1_Start (WORD): Source area or equivalent constant to be decoded
s2_Control (WORD): Control data to specify the starting bit position and number of bits to be decoded

Output

d_Start (WORD): Starting address for storing decoded data (destination)

Remarks

The variables s1_Start, s2_Control and d_Start have to be of the same data type.
Example s2_Control=16#404
1. (1) Source
2. (2) Bit position
3. (3) Bit position 4
4. (4) 4 bits (bit 4–7, binary: 2#0111 or decimal: 7) of s1_Start are decoded when the trigger is TRUE
5. (5) Destination
  The decoded data TRUE is stored in bit position 7 of d_Start.
  
  All bits except bit 7 are filled with zeros.
The contents of the 2^nL bit segment from nH bit of the area specified by s1_Start are decoded (where nL is the number of bits to be decoded).

The decoded results are stored in the 2^nL bit segments starting from the area specified by d_Start (where nH is the conversion start bit). Invalid bits in the specified area for the result are filled with zeros.

Description of s2_Control

s2_Control specifies the starting bit position and the number of bits to be decoded using hexadecimal data.

(1) 16-bit data (2) Number of bit 0–15 The bits marked "-" are invalid.
	Set value 16#0–16#F	(3) Starting bit position to be decoded	Set value 16#0–16#8	(4) Number of decoded bits
	16#0	0	16#0	0
	16#1	1	16#1	1
	16#2	2	16#2	2
	16#3	3	16#3	3
	16#4	4	16#4	4
	16#5	5	16#5	5
	16#6	6	16#6	6
	16#7	7	16#7	7
	16#8	8	16#8	8
	16#9	9
	16#A	10
	16#B	11
	16#C	12
	16#D	13
	16#E	14
	16#F	15

Relationship between number of bits and occupied data area for decoded result

Number of bits to be decoded	Data area required for the result	Number of decoded bits (result)
1	1 word	2-bit ¹⁾
2	1 word	4-bit ¹⁾
3	1 word	8-bit ¹⁾
4	1 word	16-bit
5	2 words	32-bit
6	4 words	64-bit
7	8 words	128-bit
8	16 words	256-bit

¹⁾ Invalid bits in the data area required for the result are filled with zeros.

Example of decoded data

When decoding 4-bit data, 16-bit data for the decoded result is shown below.

Decoding condition: s2_Control
Starting bit position 0: 16#0
Number of bits to be decoded: 16#4 (4 bits)

Data to be decoded (4 bits)		Decoded result
Hex.	Dec.	Decoded result
16#0000	0	0000 0000 0000 0001
16#0001	1	0000 0000 0000 0010
16#0010	2	0000 0000 0000 0100
16#0011	3	0000 0000 0000 1000
16#0100	4	0000 0000 0001 0000
16#0101	5	0000 0000 0010 0000
16#0110	6	0000 0000 0100 0000
16#0111	7	0000 0000 1000 0000
16#1000	8	0000 0001 0000 0000
16#1001	9	0000 0010 0000 0000
16#1010	10	0000 0100 0000 0000
16#1011	11	0000 1000 0000 0000
16#1100	12	0001 0000 0000 0000
16#1101	13	0010 0000 0000 0000
16#1110	14	0100 0000 0000 0000
16#1111	15	1000 0000 0000 0000

Error flags

sys_bIsOperationErrorHold (turns to TRUE and remains TRUE)

if the area specified using the index modifier exceeds the limit.
if 1 £ nL £ 8, where nL is the number of bits to be encoded/decoded.
if 1 £ nH + nL £ 16, where nH is the conversion start bit and nL is the number of bits to be encoded/decoded.
if the memory area used by the decoded result exceeds the limit.

sys_bIsOperationErrorNonHold (turns to TRUE for one scan)

if the area specified using the index modifier exceeds the limit.
if 1 £ nL £ 8, where nL is the number of bits to be encoded/decoded.
if 1 £ nH + nL £ 16, where nH is the conversion start bit and nL is the number of bits to be encoded/decoded.
if the memory area used by the decoded result exceeds the limit.

Example

POU header

All input and output variables used for programming this function have been declared in the POU header. The same POU header is used for all programming languages.

	VAR
		bStart: BOOL:=FALSE;
			(*activates the function*)
		wInput_value: WORD:=2#1100011000011110;
		wControlCode: WORD:=16#0003;
			(*specifies decoding*)
		wConversionResult: WORD:=0;
			(*result after a 0->1 leading
edge from start:
2#0000000001000000*)
	END_VAR

POU body

When the variable bStart is set to TRUE, the function is carried out.

LD body

BODY
    WORKSPACE
        NETWORK_LIST_TYPE := NWTYPELD ;
        ACTIVE_NETWORK := 0 ;
    END_WORKSPACE
    NET_WORK
        NETWORK_TYPE := NWTYPELD ;
        NETWORK_LABEL :=  ;
        NETWORK_TITLE :=  ;
        NETWORK_HEIGHT := 6 ;
        NETWORK_BODY
B(B_CONTACT,,bStart,8,1,10,3,);
B(B_VARIN,,wInput_value,11,2,13,4,);
B(B_VARIN,,wControlCode,11,3,13,5,);
B(B_VAROUT,,wConversionResult,21,2,23,4,);
B(B_F,FP_DECODE!,,13,0,21,5,,?DEN?Ds1_Start?Ds2_Control?AENO?Cd_Start);
L(10,2,13,2);
L(1,2,8,2);
L(1,0,1,6);
        END_NETWORK_BODY
    END_NET_WORK
END_BODY

ST body

IF start then
    FP_DECODE(s1_Start := wInput_value, 
              s2_Control := wControlCode, 
              d_Start => wConversionResult);
END_IF;