Chapter 28 Fault Collection Unit (FCU)
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
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After a functional reset, the FCU_FFR (not the Frozen Fault Flag Register (FCU_FFFR)) must be cleared
and the FCU must return to Normal state.
28.3.2
Output generation protocol
The FCU provides two external output signals. The FCU supports different protocols for fault indication
to the external device. Both external signals are used only in dual-rail protocol. In other protocols, the
second output is the inverted version of the first output.
In all the protocols, depending on the polarity field (PS) in the MCR, the outputs can be normal polarity
(if PS = 0) or inverted polarity (if PS = 1). The LSB of PS sets the polarity of the first signal; the MSB sets
the polarity of the second signal.
28.3.2.1
Dual-rail protocol
Dual-rail encoding is an alternate method for encoding bits. In contrast to classical encoding, where each
wire carries a single bit-value, dual-rail encoded circuits use two wires to carry each bit.
summarizes the encoding.
As long as the FCU is in Normal or Alarm state, the output shows a “non-faulty” signal. FCU[0], FCU[1]
toggles between (0,1) and (1,0) with a given frequency, set in the FOP field of the MCR. By default, this
value is f = 976 Hz @ 64 MHz (about 1 kHz, see
). The same frequency is used to show a
faulty situation (FCU in Fault state).
In the Init state, output pins are set as high impedance by clearing the OBE bits for each pad in its
respective PCR in the SIUL module.
Table 28-14. Dual-rail coding
Logical value
Dual-rail encoding (FCU[0], FCU[1])
non-faulty
(0,1)
non-faulty
(1,0)
faulty
(0,0)
faulty
(1,1)