nanoFIP status byte
bit 4: r_tler, bit 5: r_fcser
bit 4: r_tler - Consumed RP_DAT CONTROL or PDU_TYPE error or
incoherent LENGTH
bit 5: r_fcser - Consumed RP_DAT FCS or bit number error
It is important to note that the bits 4 and 5 of the nanoFIP status byte
refer only to consumed RP_DAT frames.
nanoFIP is not providing information of errors that may have been
detected in ID_DAT frames; wrong ID_DAT frames are just
ignored*.
bit 6: t_txer, bit 7: t_wder
bit 6: t_txer - Transmit error (FIELDRIVE)
bit 7: t_wder -Watchdog error (FIELDRIVE)
Bit 6 and 7 in the nanoFIP status byte are just a direct copy of the actual value of these two signals from the FielDrive driver component. These signals are not actually used by the nanoFIP. The manual of the FielDrive reads:
- A TXER signal is generated when the symbol duration exceeds tDsymb, which indicates a “stuck at fault” condition.
- A TXER signal is generated when an overload state or an underload state is monitored from the driver outputs.
- A watchdog signal WDGn is generated when the frame length exceeds tDjab, the jabber time. This signal is kept active until re-initialization of the chip with the RESETn input signal.
Reading this, and also reading the more detailed "FIELDRIVE 2 LINE DRIVER SPECIFICATION*" in possession by CERN, there is no suggestion that either TXER or WDGn would disable the transmitter of the FielDrive.
The nanoFIP does not act on these signals to prevent any blocking if the
FielDrive would ever give wrong information because of radiation
problems. The generation of these two signals is done by the "digital"
part of the FielDrive transmitter, while the "analog" main function of
the FielDrive transmitter may still perfectly work.
Actually the WDGn would only be generated if the nanoFIP would behave
badly which it should not because of its robust design. The TXER signal
may even become active if the bus is heavily loaded or other problems
that may be out of control of the station. Therefore it was considered
best to only forward these signals via the nanoFIP Status and not to try
to do anything intelligent with them.
*) \Departments\AB\Projects\worldfip\cd2_dossiers\Composants\FIELDRIVE\fieldrive3_spec(D)
_Back to the Hints n' Tips Guide_
E.Gousiou, E.van der Bij - March 2012