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S3C2410A ARM INSTRUCTION SET
3-57
TRANSFERS TO R15
When a coprocessor register transfer to ARM920T has R15 as the destination, bits 31, 30, 29 and 28 of the
transferred word are copied into the N, Z, C and V flags respectively. The other bits of the transferred word are
ignored, and the PC and other CPSR bits are unaffected by the transfer.
TRANSFERS FROM R15
A coprocessor register transfer from ARM920T with R15 as the source register will store the PC+12.
INSTRUCTION CYCLE TIMES
MRC instructions take 1S + (b+1)I +1C incremental cycles to execute, where S, I and C are defined as sequential
(S-cycle), internal (I-cycle), and coprocessor register transfer (C-cycle), respectively. MCR instructions take 1S + bI
+1C incremental cycles to execute, where b is the number of cycles spent in the coprocessor busy-wait loop.
ASSEMBLER SYNTAX
<MCR|MRC>{cond} p#,<expression1>,Rd,cn,cm{,<expression2>}
MRC Move from coprocessor to ARM920T register (L=1)
MCR Move from ARM920T register to coprocessor (L=0)
{cond} Two character condition mnemonic. See Table 3-2
p# The unique number of the required coprocessor
<expression1> Evaluated to a constant and placed in the CP Opc field
Rd An expression evaluating to a valid ARM920T register number
cn and cm Expressions evaluating to the valid coprocessor register numbers CRn and CRm
respectively
<expression2> Where present is evaluated to a constant and placed in the CP field
EXAMPLES
MRC p2,5,R3,c5,c6 ; Request coproc 2 to perform operation 5
; on c5 and c6, and transfer the (single
; 32-bit word) result back to R3.
MCR p6,0,R4,c5,c6 ; Request coproc 6 to perform operation 0
; on R4 and place the result in c6.
MRCEQ p3,9,R3,c5,c6,2 ; Conditionally request coproc 3 to
; perform operation 9 (type 2) on c5 and
; c6, and transfer the result back to R3.