Datasheet

132
AT89C51IC2
4301D–8051–02/08
AC Parameters
Explanation of the AC
Symbols
Each timing symbol has 5 characters. The first character is always a “T” (stands for
time). The other characters, depending on their positions, stand for the name of a signal
or the logical status of that signal. The following is a list of all the characters and what
they stand for.
Example:T
AVLL
= Time for Address Valid to ALE Low.
T
LLPL
= Time for ALE Low to PSEN Low.
(Load Capacitance for port 0, ALE and PSEN = 100 pF; Load Capacitance for all other
outputs = 80 pF.)
Table 94 Table 97, and Table 99 give the description of each AC symbols.
Table 96, Table 98 and Table 100 give the AC parameterfor each range.
Table 95, Table 96 and Table 101 gives the frequency derating formula of the AC
parameter for each speed range description. To calculate each AC symbols, take the x
value in the correponding column (-M or -L) and use this value in the formula.
Example: T
LLIU
for -M and 20 MHz, Standard clock.
x = 35 ns
T 50 ns
T
CCIV
= 4T - x = 165 ns
External Program Memory
Characteristics
Table 94. Symbol Description
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 Float after PSEN
T
AVIV
Address to Valid Instruction In
T
PLAZ
PSEN Low to Address Float