DS87C520 datasheet(32/45 Pages) DALLAS

32 / 45 page

DS87C520/DS83C520 EPROM/ROM High-Speed Microcontrollers

32 of 45

AC ELECTRICAL CHARACTERISTICS (Note 1)

33 MHz

VARIABLE CLOCK

PARAMETER

SYMBOL

MIN

MAX

MIN

MAX

UNITS

External Oscillator

Oscillator

Frequency

External Crystal

1/tCLCL

MHz

ALE Pulse Width

tLHLL

1.5tCLCL-5

Port 0 Address Valid to ALE Low

tAVLL

0.5tCLCL-5

Address Hold after ALE Low

tLLAX1

(Note 2)

ALE Low to Valid Instruction In

tLLIV

2.5tCLCL-33

ALE Low to PSEN Low

tLLPL

0.5tCLCL-11

PSEN

Pulse Width

tPLPH

2tCLCL-5

PSEN

Low to Valid Instruction In

tPLIV

2tCLCL-24

Input Instruction Hold after PSEN

tPXIX

Input Instruction Float after PSEN

tPXIZ

tCLCL-5

Port 0 Address to Valid Instruction In

tAVIV1

3tCLCL-32

Port 2 Address to Valid Instruction In

tAVIV2

3.5tCLCL-38

PSEN

Low to Address Float

tPLAZ

(Note 2)

Note 1:

All parameters apply to both commercial and industrial temperature range operation unless otherwise noted.

Specifications to -40°C are guaranteed by design and are not production tested. AC electrical characteristics are not

100% tested, but are characterized and guaranteed by design. All signals characterized with load capacitance of 80pF

except Port 0, ALE,

PSEN, RD, and WR with 100pF. Interfacing to memory devices with float times (turn off times)

over 25ns may cause contention. This will not damage the parts, but will cause an increase in operating current.

Specifications assume a 50% duty cycle for the oscillator. Port 2 and ALE timing will change in relation to duty cycle

variation.

Note 2:

Address is driven strongly until ALE falls, and is then held in a weak latch until overdriven externally.

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