init.fuc

/**
 * init.fuc - Basic Falcon runtime initialization.
 *
 * The initial Falcon microcode that executes on an engine must
 * initialize its own stack. This example showcases how that works.
 *
 * This works on any Falcon version!
 */

.equ #FALCON_HWCFG 0x4200
.equ #FALCON_HWCFG_DMEM_SIZE_SHIFT 0x9
.equ #FALCON_HWCFG_DMEM_SIZE_MASK  0x1FF

// Read the contents of the FALCON_HWCFG register into REG13.
mov $r13 #FALCON_HWCFG
iord $r13 I[$r13]
// Extract the bitfield that encodes the size of the DMEM in 0x100
// byte quantities and shift it by 8 to obtain its size in bytes.
shr.w $r13 #FALCON_HWCFG_DMEM_SIZE_SHIFT
and $r13 #FALCON_HWCFG_DMEM_SIZE_MASK
shl.w $r13 0x8
// Move the greatest supported address of the DMEM segment (which
// is equivalent to its size we extracted) into the stack pointer.
mov $sp $r13

/*
 * Application code here...
 */

// Halt the microprocessor after execution is done.
halt