IMPYL P,XT,loc32
6-106
IMPYL P,XT,loc32 Signed 32 X 32-Bit Multiply (Lower Half)
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
IMPYL P,XT,loc32 0101 0110 0000 0101
0000 0000 LLLL LLLL
1 − 1
Operands P Product register
XT Multiplicand register
loc32 Addressing mode (see Chapter 5)
Description Multiply the signed 32-bit content of the XT register by the signed 32-bit
content of the location pointed to by the “loc32” addressing mode. The
product shift mode (PM) then determines which part of the lower 38 bits of
the 64-bit result gets stored in the P register as shown in the diagram below:
temp(37:0) = lower_38 bits(signed XT * signed [loc32]);
if( PM = +4 shift )
P(31:4) = temp(27:0), P(3:0) = 0;
if( PM = +1 shift )
P(31:1) = temp(30:0), P(0) = 0;
if( PM = 0 shift )
P(31:0) = temp(31:0);
if( PM = −1 shift )
P(31:0) = temp(32:1);
if( PM = −2 shift )
P(31:0) = temp(33:2);
if( PM = −3 shift )
P(31:0) = temp(34:3);
if( PM = −4 shift )
P(31:0) = temp(35:4);
if( PM = −5 shift )
P(31:0) = temp(36:5);
if( PM = −6 shift )
P(31:0) = temp(37:6);
Flags and
Modes
PM The value in the PM bits sets the shift mode that determines which portion
of the lower 38 bits of the 64-bit results are stored in the P register.
Repeat This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
Example ;
Calculate signed result: Y64 = M32*X32
MOVL XT,@M32 ; XT = M32
IMPYL P,XT,@X32 ; P = low 32 bits of (M32*X32)
QMPYL ACC,XT,@X32 ; ACC = high 32 bits of (M32*X32)
MOVL @Y64+0,P ; Store result into Y64
MOVL @Y64+2,ACC
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