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ARM DDI 0363E Copyright © 2009 ARM Limited. All rights reserved. 11-69
ID013010 Non-Confidential, Unrestricted Access
}
Example 11-26 shows the sequence for writing a block of words to memory.
Example 11-26 Writing a block of words to memory (fast download)
WriteWords(uint32 address, bool &aborted, uint32 *data, int nwords)
{
// Step 1. Save the value of R0.
saved_r0 := ReadRegister(0);
// Step 2. Write the value 0b10 to DSCR[21:20] for fast mode.
SetDTRAccessMode(2);
// Step 3. Write the opcode for MRC p14, 0, R0, c5, c0 to the ITR.
// Write stalls until the ITR is ready but the instruction is not issued.
WriteDebugRegister(33, 0xEE100E15);
// Step 4. Write the address to read from to the DTRRX
// Write stalls until the ITR is ready, but the instruction is not reissued.
WriteDebugRegister(32, address);
// Step 5. Write the opcode for STC p14, c5, [R0], 4 to the ITR.
// Write stalls until the ITR is ready but the instruction is not issued.
WriteDebugRegister(33, 0xECA05E01);
// Step 6. Loop writing the data.
// Each time a word is written to the DTRRX, the instruction is reissued.
while (nwords > 0)
{
WriteDebugRegister(35, *data++);
--nwords;
}
// Step 7. Write the value b00 to DSCR[21:20] for normal mode.
SetDTRAccessMode(0);
// Step 8. Restore the corrupted register R0.
WriteRegister(0, saved_r0);
// Step 9. Check the DSCR for a sticky abort.
aborted := CheckForAborts();
}
Note
As the amount of data transferred increases, these functions reach an optimum performance of
one debug register access per data word transferred.
After writing data to memory, you must execute a data synchronization barrier instruction to
ensure that the memory window updates properly
Accessing coprocessor registers
The sequence for accessing coprocessor registers is the same for the PC and CPSR. That is, you
must first execute an instruction to transfer the register to an ARM register, then read the value
back through the DTR.
Example 11-27 shows the sequence for reading a coprocessor register.
Example 11-27 Reading a coprocessor register
uint32 ReadCPReg(int CPnum, int opc1, int CRn, int CRm, int opc2)
{