circuitpython/atmel-samd/boards/samd21x18-external-flash.ld
Scott Shawcroft e3f9ee839a Add frequency changing support to PWMOut.
You can either set it once up front, or set variable_frequency on custruction to
indicate that the frequency must be able to change. This informs whether a timer
can be shared amongst pins.

This also adds persistent clock calibration on atmel-samd. Once the device has
synced its clock frequency over USB it will remember that config value until USB
is used again. This helps ensure the clock frequency is similar on and off USB.

Lastly, this also corrects time.sleep() when on USB by correcting the tick counter.
2017-01-30 15:02:01 -08:00

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/*
GNU linker script for SAMD21
*/
/* Specify the memory areas */
MEMORY
{
FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00040000 - 0x100 /* 256 KiB but leave 256b for config */
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
}
/* top end of the stack */
_estack = ORIGIN(RAM) + LENGTH(RAM);
/* define output sections */
SECTIONS
{
/* The program code and other data goes into FLASH */
.text :
{
. = ALIGN(4);
_sfixed = .;
KEEP(*(.vectors)) /* isr vector table */
*(.text) /* .text sections (code) */
*(.text*) /* .text* sections (code) */
*(.rodata) /* .rodata sections (constants, strings, etc.) */
*(.rodata*) /* .rodata* sections (constants, strings, etc.) */
. = ALIGN(4);
_etext = .; /* define a global symbol at end of code */
} >FLASH
.ARM.exidx :
{
*(.ARM.exidx*)
*(.gnu.linkonce.armexidx.*)
_sidata = .; /* This is used by the startup in order to initialize the .data section */
} > FLASH
/* This is the initialized data section
The program executes knowing that the data is in the RAM
but the loader puts the initial values in the FLASH (inidata).
It is one task of the startup to copy the initial values from FLASH to RAM. */
.data : AT ( _sidata )
{
. = ALIGN(4);
_srelocate = .; /* create a global symbol at data start; used by startup code in order to initialise the .data section in RAM */
*(.ramfunc)
*(.ramfunc*)
*(.data) /* .data sections */
*(.data*) /* .data* sections */
. = ALIGN(4);
_erelocate = .; /* define a global symbol at data end; used by startup code in order to initialise the .data section in RAM */
} >RAM
/* Uninitialized data section */
.bss :
{
. = ALIGN(4);
_sbss = .;
_szero = .; /* define a global symbol at bss start; used by startup code */
*(.bss)
*(.bss*)
*(COMMON)
. = ALIGN(4);
_ezero = .; /* define a global symbol at bss end; used by startup code */
_ebss = .;
} >RAM
/* this just checks there is enough RAM for a minimal stack */
.stack :
{
. = ALIGN(4);
. = . + 0x800; /* Reserve a minimum of 2K for the stack. */
. = ALIGN(4);
} >RAM
.ARM.attributes 0 : { *(.ARM.attributes) }
}