AT80C51RB2-SLSCM datasheet(69/83 Pages) ATMEL

69 / 83 page

AT80C51RD2/AT83C51Rx2

4113B–8051–03/05

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:TAVLL = Time for Address Valid to ALE Low.

TLLPL = 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 49 Table 52, and Table 54 give the description of each AC symbols.

Table 51, Table 53 and Table 55 give for each range the AC parameter.

Table 50, Table 51 and Table 56 gives the frequency derating formula of the AC param-

eter 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

CCIV = 4T - x = 165 ns

External Program Memory

Characteristics

Table 49. Symbol Description

Symbol

Parameter

Oscillator clock period

LHLL

ALE pulse width

AVLL

Address Valid to ALE

LLAX

Address Hold After ALE

LLIV

ALE to Valid Instruction In

LLPL

ALE to PSEN

PLPH

PSEN Pulse Width

PLIV

PSEN to Valid Instruction In

PXIX

Input Instruction Hold After PSEN

PXIZ

Input Instruction FloatAfter PSEN

AVIV

Address to Valid Instruction In

PLAZ

PSEN Low to Address Float

AT80C51RB2-SLSCM Datasheet(PDF) 69 Page - ATMEL Corporation

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