8XC51GB

EXPLANATION OF THE AC SYMBOLS

Each timing symbol has 5 characters The first char-

acter 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

A Address

C Clock

D Input Data

H Logic Level HIGH

I Instruction (Program Memory Contents)

L Logic Level LOW or ALE

P PSEN

Q Output Data

R RD Signal

T Time

V Valid

W WR Signal

X No Longer a Valid Logic Level

Z Float

For Example

TAVLL e Time from Address Valid to ALE Low

TLLPL e Time from ALE Low to PSEN Low

AC SPECIFICATIONS

Over Operating Conditions Load Capacitance on Port 0 ALE and PSEN e 100 pF Load Capacitance on all

other outputs e 80 pF

EXTERNAL PROGRAM AND DATA MEMORY CHARACTERISTICS

Symbol

Parameter

12 MHz Osc

Variable Osc

Units

Min

Max

Min

Max

1TCLCL

Osc Freq

35

16

MHz

TLHLL

ALE Pulse Width

127

2TCLCL b 40

ns

TAVLL

ADDR Valid to ALE Low

43

TCLCL b 40

ns

TLLAX

ADDR Hold after ALE Low

53

TCLCL b 30

ns

TLLIV

ALE Low to Valid Inst IN

234

4TCLCL b 100

ns

TLLPL

ALE LOW to PSEN LOW

53

TCLCL b 30

ns

TPLPH

PSEN Pulse Width

205

3TCLCL b 45

ns

TPLIV

PSEN Low to Valid Instr In

145

3TCLCL b 105

ns

TPXIX

Input Instr Hold after PSEN

00

ns

TPXIZ

Input Instr Float after PSEN

59

TCLCL b 25

ns

TAVIV

ADDR to Valid Instr In

312

5TCLCL b 105

ns

TPLAZ

PSEN Low to ADDR Float

10

10

ns

TRLRH

RD Pulse Width

400

6TCLCL b 100

ns

TWLWH

WR Pulse Width

400

6TCLCL b 100

ns

TRLDV

RD Low to Valid Data In

252

5TCLCL b 165

ns

TRHDX

Data Hold after RD

00

ns

TRHDZ

Data Float after RD

107

2TCLCL b 60

ns

TLLDV

ALE Low to Valid Data In

517

8TCLCL b 150

ns

TAVDV

ADDR to Valid Data In

585

9TCLCL b 165

ns

TLLWL

ALE Low to RD or WR Low

200

300

3TCLCL b 50

3TCLCL a 50

ns

TAVWL

ADDR Valid to RD or WR Low

203

4TCLCL b 130

ns

TQVWX

Data Valid to WR Transition

33

TCLCL b 50

ns

TWHQX

Data Hold after WR

33

TCLCL b 50

ns

TQVWH

Data Valid to WR High

433

7 TCLCL b 150

ns

TRLAZ

RD Low to Addr Float

0

0

ns

TWHLH

RD or WR High to ALE High

43

123

TCLCL b 40

TCLCL a 40

ns

11