FIDO1100PQF208IR1 Innovasic Semiconductor Inc., FIDO1100PQF208IR1 Datasheet - Page 78

• Manufacturer Part Number: FIDO1100PQF208IR1
• Description: 32-bit Real-time Communications Controller
• Manufacturer: Innovasic Semiconductor Inc.

Flexible Input Deterministic Output (fido ® )
32-Bit Real-Time Communications Controller
Errata No. 3
Problem:
interrupt to a higher priority context.
Description
higher priority context sleeping, if an interrupt comes in for the higher priority context
simultaneously with the execution of a trapx instruction in the low priority context, it can happen
that the interrupt handler is executed by the master context (even though intended for the higher
priority context), while the trapx handler is executed by the higher priority context.
Workaround:
The workaround involves several issues:
The approach given in 3 and 4 above, while more complex than simply having the trapx
handler issue a trapx instruction if not executed in the master context, avoids the issue of
trapx handlers that rely on the Faulted Context register to determine what specific action to
take.
The Master context will be moved to the ready state, with no modification of its program
counter, thus it will start running from where it left off previously.
All other contexts are unaffected.
The vectors are reversed when a trapx instruction is executed coincident with an
1. Any interrupt handlers intended for other than the lowest priority context should
2. The master context must have a valid vector to the appropriate interrupt handlers.
3. Trapx handlers should verify that they are being executed in the master context.
4. The routine executing a trapx instruction should check the handshake flag from
: Given a low priority context currently executing and the master context and a
be executable by the master context.
Either the master context and the other contexts share a vector table or the vectors
are duplicated on the master context's table. If the master context is executed in a
different mode than the other contexts (e.g. master in standard mode, other
context in fast-vectored mode), then a second interrupt handler must be coded that
is compatible with the master context's operating mode.
This assumes that they are performing some action that can only be executed in
the master context, and if so, then they should execute and set a flag to alert the
caller that they executed. If not, then they should return without setting the flag.
Also, trapx handlers must be present (in the appropriate execution mode) on all
vector tables.
the trapx handler after execution of the instruction. If it is not set appropriately,
the trapx should be executed again.
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IA211080807-06
November 20, 2009
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