Siemens SIMATIC S5 Manual page 219

Function
Notes on processing errors
If the error byte (FY255) is to be evaluated, it must be saved on the rising edge of the parameter
PAFE in a different data area after FB 162 has been called.
Reason: scratchpad flag area of flag byte FY200 to FY255
when PAFE ––––> FY255
Notes on specifying the actual operands
The identifiers ANST (I,BI) and NEUA, PAFE, AFEH, BFEH and SFEH (Q,BI) must not have the
scratchpad flags written to them.
The identifiers KANR (Q,BI) and FMLD (Q,W) must also not have the scratchpad flags of the
function block FB162 written to them.
5–14
Bit assignment of parameter FMLD:
Bits 0 to 7: error byte from message 16
Bits 8 to 15: error byte from message 46
parameter assignment error
IP244
C79000–B8576–C861–02