Texas Instruments TMS320C28x, Reference Manual

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XPREAD loc16, *(pma)
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XPREAD loc16, *(pma) C2xLP Source-Compatible Program Read
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
XPREAD loc16,*(pma)
1010 1100 MMMM MMMM
LLLL LLLL LLLL LLLL
1 Y N+2
Operands loc16 Addressing mode (see Chapter 5)
*(pma) Immediate program-memory address, can only access high 64K of program
space range (0x3F0000 to 0x3FFFFF)
Description Load the 16-bit data-memory location pointed to by the “loc16” addressing
mode with the 16-bit content of the program-memory location pointed to by
”*(pma)” addressing mode:
[loc16] = Prog[0x3F:pma];
The C28x forces the upper 6 bits of the program memory address, specified
by the ”*(pma)” addressing mode, to 0x3F when using this form of the
XPREAD instruction. This limits the program memory address to the high
64K of program address space (0x3F0000 to 0x3FFFFF). On the C28x
devices, memory blocks are mapped to both program and data space
(unified memory), hence the ”*(pma)” addressing mode can be used to
access data space variables that fall within its address range.
Flags and
Modes
N
If (loc16 = @AX) and bit 15 of AX is 1, then N is set; otherwise N is cleared.
Z If (loc16 = @AX) and the value of AX is zero, then Z is set; otherwise Z is
cleared.
Repeat This instruction is repeatable. If the operation follows a RPT instruction, then
it will be executed N+1 times. When repeated, the ”*(pma)”
program-memory address is copied to an internal shadow register and the
address is post-incremented by 1 during each repetition.
Example
; Copy the contents of Array1 to Array2:
; int16 Array1[N];
// Located in high 64K of program space
; int16 Array2[N]; // Located in data space
; for(i=0; i < N; i++)
; Array2[i] = Array1[i];
MOVL XAR2,#Array2 ; XAR2 = pointer to Array2
RPT #(N−1) ; Repeat next instruction N times
||XPREAD *XAR2++,*(Array1) ; Array2[i] = Array1[i],
; i++