21

AT89LS51

3053A–8051–05/02

AC Characteristics

Under operating conditions, load capacitance for Port 0, ALE/PROG, and PSEN = 100 pF; load capacitance for all other

outputs = 80 pF.

External Program and Data Memory Characteristics

Symbol

Parameter

16 MHz Oscillator

Variable Oscillator

Units

Min

Max

Min

Max

1/t

CLCL

Oscillator Frequency

0

16

MHz

t

LHLL

ALE Pulse Width

85

2t

ns

Address Valid to ALE Low

22

ns

Address Hold After ALE Low

32

ns

ALE Low to Valid Instruction In

150

ns

t

LLPL

ALE Low to PSEN Low

32

t

ns

t

PLPH

PSEN Pulse Width

142

3t

ns

t

PLIV

PSEN Low to Valid Instruction In

82

3t

ns

Input Instruction Hold After PSEN

00

ns

Input Instruction Float After PSEN

37

ns

PSEN to Address Valid

75

ns

t

AVIV

Address to Valid Instruction In

207

5t

ns

t

PLAZ

PSEN Low to Address Float

10

10

ns

t

RLRH

RD Pulse Width

275

6t

ns

WR Pulse Width

275

ns

RD Low to Valid Data In

147

ns

Data Hold After RD

00

ns

Data Float After RD

65

ns

t

LLDV

ALE Low to Valid Data In

350

8t

ns

t

AVDV

Address to Valid Data In

397

9t

ns

ALE Low to RD or WR Low

137

239

ns

Address to RD or WR Low

122

ns

Data Valid to WR Transition

13

ns

Data Valid to WR High

287

ns

t

WHQX

Data Hold After WR

13

t

ns

t

RLAZ

RD Low to Address Float

0

0

ns

RD or WR High to ALE High

23

103

ns