VisualDSP++ 4.5 Loader and Utilities Manual - Analog Devices

ADSP-2126x/2136x/2137x Processor Booting
block header. Instead, the 32-bit count and address words are used
to hold the instruction that overwrites the RTI inserted into the
IVT. Listing 5-1 illustrates the block header for FINAL_INIT if, for
example, the opcode 0xAABBCCDDEEFF is assumed to be the
user-intended instruction for the IVT.
Listing 5-2. FINAL_INIT Block Header Format
0x00000000 /* FINAL_INIT tag = 0x0 */
0xEEFF0000 /* LSBs of instructions */
0xAABBCCDD /* 4 MSBs of instructions */
Listing 5-3. FINAL_INIT Section
/* ====================== FINAL_INIT ======================== */
/* The FINAL_INIT subroutine in the boot kernel program sets up a
DMA to overwrite itself. The code is the very last piece that
runs in the kernel; it is self-modifying code, It uses a DMA
to overwrite itself, initializing the 256 instructions that
reside in the Interrupt Vector Table. */
/* ---------------------------------------------------------- */
final_init:
/* ----------- Setup for IVT instruction patch ------------- */
I8=0x80030; /* Point to SPI vector to patch from PX */
R9=0xb16b0000; /* Load opcode for “PM(0,I8)=PX” into R9 */
PX=pm(0x80002); /* User instruction destined for 0x80030
is passed in the section-header for
FINAL_INIT. That instr. is initialized upon
completion of this DMA (see comments below)
using the PX register. */
R11=BSET R11 BY 9; /* Set IMDW to 1 for inst. write */
DM(SYSCTL)=R11; /* Set IMDW to 1 for inst. write */
5-30 VisualDSP++ 4.5 Loader and Utilities Manual