F1 Y - Lucent Technologies DSP1617 Information Manual

Information Manual
April 1998

F1 Y

(multiply/ALU operation with postmodification of pointer register)
perform operation F1 and
access *rM; then
postmodify rM (the contents of *rM are not written to a destination)
This instruction performs the following three operations effectively in parallel:
1. The operation F1 is performed. The possible F1 operations are as follows:
F1 Operation
0000 aD = pp = x * y
0001 aD = aS + pp = x * y
0010 p = x * y
0011 aD = aS – pp = x * y
0100 aD = p
0101 aD = aS + p
The value of S can be zero to select a0 or one to select a1. The value of D can be zero to select a0 or one to
select a1. Flags are modified based on the value computed by the DAU.
Note: For all diadic operations involving the y register, y is sign-extended to 36 bits before performing the
operation including logical operations. (See
shifting the output of the p register into aS in the above operations.)
2. Access the Y-space location pointed to by rM where rM is specified by the two most significant bits of the Y
field as follows (the accessed location is not written to a destination):
00 - r0
Postmodify the value of rM where the postmodification is specified by the two least significant bits of the Y field.
2 LSBs of Y
00 no action
01 postincrement
10 postdecrement
†
11 postincrement by (j)
† Code 11, in this case, means add the current value of the j regis-
ter to rM after accessing *rM.
Note: When code 10 (postdecrement) is specified, this instruction is noninterruptible. It is used to implement the
pop(*rM) instruction.
Lucent Technologies Inc.
DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
F1
0110
0111
1000
1001
1010
01 - r1
Action Symbol
*rM
*rM++
*rM– –
*rM++j
DRAFT COPY
Operation
nop
aD = aS – p
aD = aS | y
aD = aS ^ y
aS & y
Section 3.3, Arithmetic and
10 - r2
Instruction Set Summary
F1 Operation
1011 aS – y
1100 aD = y
1101 aD = aS + y
1110 aD = aS & y
1111 aD = aS – y
Precision, for the options of
11 - r3
B-20