31
4428E–8051–02/08
AT/TS80C31X2
Table 14-7., Table 14-10. and Table 14-13. give the frequency derating formula of the AC
parameter. To calculate each AC symbols, take the x value corresponding to the speed grade
you need (-M, -V or -L) and replace this value in the formula. Values of the frequency must be
limited to the corresponding speed grade:
Table 14-4. Max frequency for derating formula regarding the speed grade
Example:
T
LLIV
in X2 mode for a -V part at 20 MHz (T = 1/20
E6
= 50 ns):
x= 25 (Table 14-7.)
T= 50ns
T
LLIV
= 2T - x = 2 x 50 - 25 = 75ns
Table 14-5. External Program Memory Characteristics
-M X1 mode -M X2 mode -V X1 mode -V X2 mode -L X1 mode -L X2 mode
Freq (MHz) 40 20 40 30 30 20
T (ns) 25 50 25 33.3 33.3 50
Symbol Parameter
T Oscillator clock period
T
LHLL
ALE pulse width
T
AVLL
Address Valid to ALE
T
LLAX
Address Hold After ALE
T
LLIV
ALE to Valid Instruction In
T
LLPL
ALE to PSEN
T
PLPH
PSEN Pulse Width
T
PLIV
PSEN to Valid Instruction In
T
PXIX
Input Instruction Hold After PSEN
T
PXIZ
Input Instruction FloatAfter PSEN
T
PXAV
PSEN to Address Valid
T
AVIV
Address to Valid Instruction In
T
PLAZ
PSEN Low to Address Float
