FTAM/9000 Reference Manual

Chapter 2 65
HP vendor_codes
inout_dcb->result.vendor_code
MESSAGE FTV421_NOT_IN_DATA_TRANS_PHASE
CAUSE You called ft_rdata() while in a regime other than data
transfer.
ACTION Call ft_rdata() in the Data Transfer regime only after
an ft_read() request and before the transferring of data
ends.