AN2556 datasheet(31/35 Pages) STMICROELECTRONICS

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AN2556

Electrical characteristics

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5.2

AC characteristics at 40 MHz

As the technology is different for the two devices, the I/Os present some differences in AC

behavior. Table 20 and Table 21 below list all the timing differences. Please carefully check

your design for any possible impacts.

5.2.1

External memory bus timings

Note that for CPU clock frequencies above 40 MHz (when using the ST10F273Z4Q3), some

numbers in the timing formulas become zero or negative. In most cases this is not

acceptable or meaningful. In such cases, it is necessary to relax the speed of the bus setting

properly tA (ALE extension), tC (Memory Cycle Time wait-states) and tF (Memory tri-state

time).

VOLCC

Output low voltage

0.45; IOL =

2.4mA

0.4; IOL = 8mA

PORT0, PORT1,

Port 4, ALE, RD,

WR, BHE,

CLKOUT, RSTOUT

PORT6, ALE,

CLKOUT, WR,

BHE, RD, RSTOUT,

RSTIN, READY

0.05; IOL =

1mA

VOL1CC

Output low voltage

(all other outputs)

0.45; IOL =

2.4mA

0.4; Iol = 4mA

0.05; IOL =

0.5mA

VOHCC

Output high voltage

0.9VDD; IOH =

-0.5mA

VDD - 0.8/ IOH =

-8mA

2.4; IOH = -2.4mA

PORT0,

PORT1, Port

4, ALE, RD,

WR, BHE,

CLKOUT,

RSTOUT

VDD -0.08/ IOH =

-1mA

PORT6, ALE,

CLKOUT, WR,

READY, BHE,

RD, RSTOUT,

RSTIN

VOH1CC

Output high voltage

(all other outputs)

0.9VDD; IOH =

-0.25mA

VDD - 0.8; IOH =

-4mA

-V

2.4; IOH = -1.6mA

VDD - 0.08; IOH =

-0.5mA

IOZ1CC

Port5 Input leakage

current

±0.5

±0.2

µA

IOZ2CC

Input leakage

current (all other

inputs)

-±1

±0.5

µA

Table 19.

DC characteristics (continued)

Symbol

Parameter

ST10F269Zx limit values

ST10F273Z4 limit values

Unit

Min

Max

Min

Max

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