GX1 Datasheet, PDF (238/247 Pages) National Semiconductor (TI) – Processor Series Low Power Integrated x86 Solution

Instruction Set (Continued)
Table 8-29. FPU Instruction Set Summary (Continued)
FPU Instruction
FSUBRP Floating Point Subtract Reverse, Pop
FISUB Floating Point Integer Subtract
32-bit Integer
16-bit Integer
FISUBR Floating Point Integer Subtract Reverse
32-bit Integer Reversed
16-bit Integer Reversed
FTST Test Top of Stack
FUCOM Unordered Compare
FUCOMP Unordered Compare, Pop
FUCOMPP Unordered Compare, Pop two
elements
FWAIT Wait
FXAM Report Class of Operand
FXCH Exchange Register with TOS
FXTRACT Extract Exponent
Opcode
DE [1110 0 n]
DA [mod 100 r/m]
DE [mod 100 r/m]
DA [mod 101 r/m]
DE [mod 101 r/m]
D9 E4
DD [1110 0 n]
DD [1110 1 n]
DA E9
9B
D9 E5
D9 [1100 1 n]
D9 F4
FLY2X Function Eval. y × Log2(x)
FLY2XP1 Function Eval. y × Log2(x+1)
D9 F1
D9 F9
Operation
ST(n) <--- TOS - ST(n); then pop TOS
TOS <--- TOS - M.SI
TOS <--- TOS - M.WI
TOS <--- M.SI - TOS
TOS <--- M.WI - TOS
CC set by TOS - 0.0
CC set by TOS - ST(n)
CC set by TOS - ST(n); then pop TOS
CC set by TOS - ST(I); then pop TOS and ST(1)
Wait for FPU not busy
CC <--- Class of TOS
TOS <--> ST(n) Exchange
temp <--- TOS;
TOS <--- exponent (temp); then
push significant (temp) onto stack
ST(1) <--- ST(1) × Log₂(TOS); then pop TOS
ST(1) <--- ST(1) × Log₂(1+TOS); then pop TOS
Clock
Count
4-9
14 - 29
14 - 27
14 - 29
14 - 27
4
4
4
4
2
4
3
11 - 16
145 - 154
131 - 133
Issue
4
FPU Instruction Summary Issues
All references to TOS and ST(n) refer to stack layout prior
to execution. Values popped off the stack are discarded.
A pop from the stack increments the top of stack pointer.
A push to the stack decrements the top of stack pointer.
Issues:
1. For FCOS, FSIN, FSINCOS and FPTAN, time shown
is for absolute value of TOS < 3p/4. Add 90 clock
counts for argument reduction if outside this range.
For FCOS, clock count is 141 if TOS < π/4 and clock
count is 92 if π/4 < TOS > π/2.
For FSIN, clock count is 81 to 82 if absolute value of
TOS < π/4.
2. For F2XM1, clock count is 92 if absolute value of TOS
< 0.5.
3. For FPATAN, clock count is 97 if ST(1)/TOS < π/32.
4. For FYL2XP1, clock count is 170 if TOS is out of range
and regular FYL2X is called.
5. The following opcodes are reserved:
D9D7, D9E2, D9E7, DDFC, DED8, DEDA, DEDC,
DEDD, DEDE, DFFC.
If a reserved opcode is executed, and unpredictable
results may occur (exceptions are not generated).
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