From 72a62ad88f82fe1ffee50024db4dd0f3fa5806f7 Mon Sep 17 00:00:00 2001 From: Chris Johns Date: Thu, 3 Nov 2016 16:58:08 +1100 Subject: Rename all manuals with an _ to have a -. It helps released naming of files. --- cpu_supplement/atmel_avr.rst | 136 ------------------------------------------- 1 file changed, 136 deletions(-) delete mode 100644 cpu_supplement/atmel_avr.rst (limited to 'cpu_supplement/atmel_avr.rst') diff --git a/cpu_supplement/atmel_avr.rst b/cpu_supplement/atmel_avr.rst deleted file mode 100644 index 6a3ce02..0000000 --- a/cpu_supplement/atmel_avr.rst +++ /dev/null @@ -1,136 +0,0 @@ -.. comment SPDX-License-Identifier: CC-BY-SA-4.0 - -.. COMMENT: COPYRIGHT (c) 1988-2006. -.. COMMENT: On-Line Applications Research Corporation (OAR). -.. COMMENT: All rights reserved. - -Atmel AVR Specific Information -############################## - -This chapter discusses the AVR architecture dependencies in this port of RTEMS. - -**Architecture Documents** - -For information on the AVR architecture, refer to the following documents -available from Atmel. - -TBD - -- See other CPUs for documentation reference formatting examples. - -CPU Model Dependent Features -============================ - -CPUs of the AVR 53X only differ in the peripherals and thus in the device -drivers. This port does not yet support the 56X dual core variants. - -Count Leading Zeroes Instruction --------------------------------- - -The AVR CPU has the XXX instruction which could be used to speed up the find -first bit operation. The use of this instruction should significantly speed up -the scheduling associated with a thread blocking. - -Calling Conventions -=================== - -Processor Background --------------------- - -The AVR architecture supports a simple call and return mechanism. A subroutine -is invoked via the call (``call``) instruction. This instruction saves the -return address in the ``RETS`` register and transfers the execution to the -given address. - -It is the called funcions responsability to use the link instruction to reserve -space on the stack for the local variables. Returning from a subroutine is -done by using the RTS (``RTS``) instruction which loads the PC with the adress -stored in RETS. - -It is is important to note that the ``call`` instruction does not automatically -save or restore any registers. It is the responsibility of the high-level -language compiler to define the register preservation and usage convention. - -Register Usage --------------- - -A called function may clobber all registers, except RETS, R4-R7, P3-P5, FP and -SP. It may also modify the first 12 bytes in the caller's stack frame which is -used as an argument area for the first three arguments (which are passed in -R0...R3 but may be placed on the stack by the called function). - -Parameter Passing ------------------ - -RTEMS assumes that the AVR GCC calling convention is followed. The first three -parameters are stored in registers R0, R1, and R2. All other parameters are -put pushed on the stack. The result is returned through register R0. - -Memory Model -============ - -The AVR family architecutre support a single unified 4 GB byte address space -using 32-bit addresses. It maps all resources like internal and external memory -and IO registers into separate sections of this common address space. - -The AVR architcture supports some form of memory protection via its Memory -Management Unit. Since the AVR port runs in supervisior mode this memory -protection mechanisms are not used. - -Interrupt Processing -==================== - -Discussed in this chapter are the AVR's interrupt response and control -mechanisms as they pertain to RTEMS. - -Vectoring of an Interrupt Handler ---------------------------------- - -TBD - -Disabling of Interrupts by RTEMS --------------------------------- - -During interrupt disable critical sections, RTEMS disables interrupts to level -N (N) before the execution of this section and restores them to the previous -level upon completion of the section. RTEMS uses the instructions CLI and STI -to enable and disable Interrupts. Emulation, Reset, NMI and Exception -Interrupts are never disabled. - -Interrupt Stack ---------------- - -The AVR Architecture works with two different kind of stacks, User and -Supervisor Stack. Since RTEMS and its Application run in supervisor mode, all -interrupts will use the interrupted tasks stack for execution. - -Default Fatal Error Processing -============================== - -The default fatal error handler for the AVR performs the following -actions: - -- disables processor interrupts, - -- places the error code in *r0*, and - -- executes an infinite loop (``while(0);`` to - simulate a halt processor instruction. - -Symmetric Multiprocessing -========================= - -SMP is not supported. - -Thread-Local Storage -==================== - -Thread-local storage is not supported due to a broken tool chain. - -Board Support Packages -====================== - -System Reset ------------- - -TBD -- cgit v1.2.3