VS1001K
VLSI
DATASHEET
y
Solution
9. WRITING SOFTWARE
If the user wants to take control away from the standard decoder, the first instruction should be replaced
with an appropriate jump command to user’s own code.
Unless the user is feeding MP3 data at the same time, the system activates the user program in less than
1 ms. After this, the user should steal interrupt vectors from the system, and then insert user programs.
9.6 System Vector Functions
The System Vector Functions are pointers to some functions that the user may call to help implementing
his own applications.
9.6.1 WriteIRam(), 0x4010
VS DSP C prototype:
void WriteIRam(register i0 u int16 *addr, register a1 u int16 msW, register a0 u int16 lsW);
This is the only supported way to write to the User Instruction RAM. This is because Instruction RAM
cannot be written when program control is in RAM. Thus, the actual implementation of this function is
in ROM, and here is simply a tag to that routine.
Note: Instruction RAM is shadowed 0x4000 addresses higher in the X and Y RAMs. Thus, if you want
to write to instruction address 0x4020,
must be 0x4020 + 0x4000 = 0x8020.
9.6.2 ReadIRam(), 0x4011
VS DSP C prototype:
u int32 ReadIRam(register i0 u int16 *addr);
This is the only supported way to read from the User Instruction RAM. This is because Instruction RAM
cannot be read when program control is in RAM. Thus, the actual implementation of this function is in
ROM, and here is simply a tag to that routine.
A1 contains the MSBs and a0 the LSBs of the result.
Note: Instruction RAM is shadowed 0x4000 addresses higher in the X and Y RAMs. Thus, if you want
to read from instruction address 0x4020,
must be 0x4020 + 0x4000 = 0x8020.
Version 4.11, 2003-09-18
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ETC [ ETC ]
