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173
Versi on 0. 4, March/2000
Purpose:
To test general register GR[r] 16-bit overflow, then saturate GR[r] into G[t],
GR r and Gr t may be the same register
Description:
To test general GR[r] 16-bit overflow, and if the general register GR[r] is overflow,
then saturate the general register GR[r], and the saturation result is put into destination register
Gr[t]. If Gr[r] is not overflow, the GR[r] value is copied into GR[t].
The saturation instruction for GR[r] is intended to be used in the 16-bit halfword
operation, and the result is stored in GR r register. The operation tests the high-order 32-bits of
the register GR[r], and the possible results after execution of saturation is shown in TableI.
Taable I..
*HOV GR[r]{0}
0
0
No change
0
1 No change
1
0
32h0000_7FFF
1
1 32hFFFF_8000
*HOV : HOV is set when the high-order 17-bits of GR[r] register are not all the same.
Operation:
if(HOV) GR[t]{0:31}
←
{{17{GR[r]{0}}}, {15{~GR[r]{0}}}};
break;
Exception :
None
* Note : 16-bit halfword operation in PA-Architecture 32-bit operation. The MSB 16-bits should be
sign_extented previously.
Derive Exponent
EXP
Format:
EXP, r, t
0:5 6:10 11:15 16:18 19 20 21:25
26 27:31
05
~
r
~
~
1
0d
~
t
6 5 5 3 1
1 5 1 5
Purpose:
To derive the effective exponent of the operand GR[r] into GR[t].
Description:
The EXP operation derives the effective exponent of the input operand to prepare
for normalization. Generally speaking, Normalization can be divided into two-stage. The first
stage derives the effective exponent. The second stage does the actually shifting. The first uses
EXP instruction which detects the exponent value and load it into GR[t]. The second stage uses
the shift relative instruction to shift GR[r] by the shift amount of GR[t].