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@c
@c COPYRIGHT (c) 2014 Hesham ALMatary <heshamelmatary@gmail.com>
@c All rights reserved.
@ifinfo
@end ifinfo
@chapter OpenRISC 1000 Specific Information
This chapter discusses the
@uref{http://opencores.org/or1k/Main_Page, OpenRISC 1000 architecture}
dependencies in this port of RTEMS. There are many implementations
for OpenRISC like or1200 and mor1kx. Currently RTEMS supports basic
features that all implementations should have.
@subheading Architecture Documents
For information on the OpenRISC 1000 architecture refer to the
@uref{http://openrisc.github.io/or1k.html,OpenRISC 1000 architecture manual}.
@section Calling Conventions
Please refer to the
@uref{http://openrisc.github.io/or1k.html#__RefHeading__504887_595890882,Function Calling Sequence}.
@subsection Floating Point Unit
A floating point unit is currently not supported.
@section Memory Model
A flat 32-bit memory model is supported.
@section Interrupt Processing
OpenRISC 1000 architecture has 13 exception types:
@itemize @bullet
@item Reset
@item Bus Error
@item Data Page Fault
@item Instruction Page Fault
@item Tick Timer
@item Alignment
@item Illegal Instruction
@item External Interrupt
@item D-TLB Miss
@item I-TLB Miss
@item Range
@item System Call
@item Floating Point
@item Trap
@end itemize
@subsection Interrupt Levels
There are only two levels: interrupts enabled and interrupts disabled.
@subsection Interrupt Stack
The OpenRISC RTEMS port uses a dedicated software interrupt stack.
The stack for interrupts is allocated during interrupt driver initialization.
When an interrupt is entered, the _ISR_Handler routine is responsible for
switching from the interrupted task stack to RTEMS software interrupt stack.
@section Default Fatal Error Processing
The default fatal error handler for this architecture performs the
following actions:
@itemize @bullet
@item disables operating system supported interrupts (IRQ),
@item places the error code in @code{r0}, and
@item executes an infinite loop to simulate a halt processor instruction.
@end itemize
@section Symmetric Multiprocessing
SMP is not supported.
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