AN2549

Electrical characteristics

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5.2

AC characteristics at 40 MHz

As the two devices have a different technology, the I/Os also present some differences in the

AC behavior. The tables below (Table 20 and Table 21) list all the timing differences. Please

check carefully your design for possible impact.

5.2.1

External memory bus timings

Note that for CPU clock frequencies above 40 MHz (for ST10F272Z2Q3 devices), some

numbers in the timing formulas become zero or negative, that in most of the cases is not

acceptable or not meaningful at all. In these cases, it is necessary to reduce the speed of

(Memory tri-state time).

Output low

voltage

–

Port0, Port1, Port4,

ALE, RD, WR, BHE,

CLKOUT, RSTOUT

2.4mA

–

Port6, ALE,

CLKOUT, WR,

READY, BHE, RD,

RSTOUT, RSTIN

V

Output low

voltage (all

other)

2.4mA

0.05 /

V

Output high

voltage

-0.5mA

–

Port0, Port1,

Port4, RD, ALE,

BHE, WR,

CLKOUT,

RSTOUT

-8mA

-1mA

–

Port6, ALE,

CLKOUT, WR,

READY, BHE,

RD, RSTOUT,

RSTIN

V

Output high

voltage (all

other)

-0.25mA

–

-4mA

-0.5mA

–V

Input leakage

current (Port 5)

–

±0.5

–

±0.2

µA

Input leakage

current (all other

inputs)

–±1

–

±0.5

µA

Table 19.

DC characteristics (continued)

Symbol

Parameter

ST10F269Zx Limit values

ST10F272Z2 Limit values

Unit

Min

Max

Min

Max