NS32FV16 Datasheet, PDF (94/104 Pages) Texas Instruments – Advanced Imaging/Communication Signal Processors

Appendix B Instruction Execution Times (Continued)
TOPi If operand is in a register or is immediate then
TOPi e 0
B 1 3 Calculation of the Execution Time TEX for
Basic Instructions
else if i e byte then TOPi e TOPB
The execution time for a basic instruction is obtained by
else if i e word then TOPi e TOPW
performing the following steps
else (i e double-word) then TOPi e TOPD
1 Find the desired instruction in Table B-1
L If i (operation length) e byte then L e 1
else if i e word then L e 2
else (i e double-word) L e 4
f If standard floating (32 bits) f e 1
2 Calculate the values of TEA TOPB etc using the num-
bers in the table and the equations given in the previous
sections
3 The result derived by adding together these values is the
execution time TEX in clock cycles
If long floating (64 bits) f e 2
EXAMPLE
Tf Tf e 4
Calculate TEX for the instruction CMPW R0 TOS
Ti If integer e byte or word then Ti e 2
Operand 1 is in a register Operand 2 is in memory This
If integer e double-word then Ti e 4
means that we must use the table values corresponding to
B 1 2 Notes on Table Use
Values in the TEA1 and TEA2 columns indicate whether
effective addresses need to be calculated
A value of 1 indicates that address calculation time is re-
quired for the corresponding operand A 0 indicates that the
operand is either missing or it is in a register and the in-
struction has an optimized form which eliminates the TEA
calculation for it
x ^{te In the L column multiply the entry by the operation length in}
bytes (1 2 or 4)
In the TCY column special notations sometimes appear
n1
n2 means n1 minimum n2 maximum
n1%n2 means that the instruction flushes the instruction
queue after n1 clock cycles and nonsequentially fetches the
le ^{next instruction The value n2 indicates the number of clock}
cycles for the internal execution of the instruction (including
n1)
The effective number of cycles (TCY) must take into ac-
count the time (T_fetch) required to fetch the portion of the
next instruction including the basic encoding and the index
bytes This time depends on the size and the alignment of
o ^{this portion}
If only one memory cycle is required then
TCY e n1 a 6 a T_fetch
If more than one memory cycle is required then
s _TCY e _n1 a ₅ a _Tfetch
In the notes column notations held within angle brackets
k l _{indicate alternatives in the operand addressing modes}
which affect the execution time A table entry which is af-
fected by the operand addressing may have multiple values
b _{corresponding to the alternatives These addressing nota-}
tions are
k_Il _Immediate
k_Rl _{CPU Register}
k_Ml _Memory
O ^{kFl FPU Register either 32 or 64 Bits}
the ^kxM^l case as given in the Notes column
Only the TEA1 TEA2 TOPi and TCY columns have
values assigned for the CMPi instruction Therefore they
are they only ones that need to be calculated to find TEX
The blank columns are irrelevant to this instruction
Both TEA1 and TEA2 columns contain 1 for the ^kxM^l
case This means that effective address times have to be
calculated for both operands (For the ^kMR^l case the
Register operand would have required no TEA time there-
fore only the Memory operand TEA would have been neces-
sary ) From the equations
TEA1 (Register mode) e 2
TEA2 (Top of Stack mode access class read) e 2
The TOPi column represents potential operand transfers
to or from memory For a Compare instruction each oper-
and is read once for a total of two operand transfers
TOPi (Word Register) e 0
TOPi (Word TOS) e 3 (assuming the operand aligned)
Total TOPi e 3
TCY is the time required for internal operation within the
CPU The TCY value for this case is 3
TEX e TEA1 a TEA2 a TOPi a TCY e 2 a 2 a 3 a 3
e 10 machine cycles
If the CPU is running at 20 MHz then a machine cycle (clock
cycle) is 50 ns Therefore this instruction would take 10 c
50 ns or 0 5 ms to execute
B 1 4 Calculation of the Execution Time TEX for
Floating-Point Instructions
The execution time for a floating-point instruction is ob-
tained by performing the following steps
1 Find the desired instruction in Table B-2
2 Calculate the values of TEA1 TEA2 TOPB etc using
the numbers in the table and the equations given in the
previous sections
3 Get the floating-point instruction execution time TFPU
from the appropriate FPU data sheet
4 Choose the higher value between TPR and TFPU a 3
k_xl _{Any Addressing Mode}
5 The result derived by adding together these values is the
k_abl _{a and b represent the addressing modes of operand}
execution time TEX in clock cycles
1 and 2 respectively Both a and b can be any ad-
dressing mode (e g ^kMR^l means memory to CPU
EXAMPLE 1
register)
Calculate TEX for the instruction MOVLF F0 h 3000
Note Unless otherwise specified the TCY value for immediate addressing is
the same as for CPU register addressing
Assumptions
 The FPU being used is the NS32181
 Write cycles are performed with no wait states
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