CMVPFB01A
28
Acyclic Parameter Access
6.3 Modes 1 & 2 - 4WPA Format
The 4WPA format of acyclic parameter data access is a simple method that utilises 4 words of cyclic data
which can be placed either before the regular cyclic data or after depending on the users preference or
application requirements. 4WPA is comprised of 4 words of data.
Table 26: 4WPA Format
Word
Byte
Function
0
0
Function Code
1
Access Control & Status
1
2
Parameter Number
Byte 2 = MSB
3
Byte 3 = LSB
2
4
Sub-Index
5
Data Word
Byte 5 = MSB
3
6
Byte 6 = LSB
7
Reserved
6.3.1 4WPA - Function Code (Byte 0)
The purpose of the Function Code is to provide control and status information of the acyclic data.
Table 27: 4WPA Function Code
Bit
Description
0
Note: 0, 3 & 6 are Decimal Values
0 = Idle Message
3 = Read Parameter
6 = Write Parameter
1
2
3
4
5
6
7
0 = No Fault
1 = Fault, Access Failure, See Access Control
