30

1919D–MICRO–6/08

AT89S52

28. AC Characteristics

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

outputs = 80 pF.

28.1

External Program and Data Memory Characteristics

Symbol

Parameter

12 MHz Oscillator

Variable Oscillator

Units

Min

Max

Min

Max

Oscillator Frequency

0

33

MHz

t

LHLL

ALE Pulse Width

127

2t

ns

Address Valid to ALE Low

43

ns

Address Hold After ALE Low

48

ns

t

LLIV

ALE Low to Valid Instruction In

233

4t

ns

ALE Low to PSEN Low

43

ns

PSEN Pulse Width

205

ns

t

PLIV

PSEN Low to Valid Instruction In

145

3t

ns

Input Instruction Hold After PSEN

00

ns

Input Instruction Float After PSEN

59

ns

t

PXAV

PSEN to Address Valid

75

t

ns

Address to Valid Instruction In

312

ns

PSEN Low to Address Float

10

10

ns

t

RLRH

RD Pulse Width

400

6t

ns

WR Pulse Width

400

ns

t

RLDV

RD Low to Valid Data In

252

5t

ns

t

RHDX

Data Hold After RD

00

ns

Data Float After RD

97

ns

t

LLDV

ALE Low to Valid Data In

517

8t

ns

t

AVDV

Address to Valid Data In

585

9t

ns

ALE Low to RD or WR Low

200

300

ns

t

AVWL

Address to RD or WR Low

203

4t

ns

t

QVWX

Data Valid to WR Transition

23

t

ns

Data Valid to WR High

433

ns

t

WHQX

Data Hold After WR

33

t

ns

t

RLAZ

RD Low to Address Float

0

0

ns

RD or WR High to ALE High

43

123

ns