
63
4113D–8051–01/09
AT80C51RD2
Figure 17-4. Clock Signal Waveform for I
CC Tests in Active and Idle Modes
17.3
AC Parameters
17.3.1
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 sta-
tus 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.)
ter for each speed range description. To calculate each AC symbols. take the x value in the
correponding column and use this value in the formula.
Example: T
LLIU for 20 MHz, Standard clock.
x = 35 ns
T = 50 ns
T
CCIV = 4T - x = 165 ns
V
CC-0.5V
0.45V
0.7V
CC
0.2V
CC-0.1
T
CLCH
T
CHCL
T
CLCH = TCHCL = 5ns.