ST7232A datasheet(118/154 Pages) STMICROELECTRONICS

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ST7232A

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12.5 CLOCK AND TIMING CHARACTERISTICS

Subject to general operating conditions for VDD, fCPU, and TA.

12.5.1 General Timings

12.5.2 External Clock Source

Figure 62. Typical Application with an External Clock Source

Notes:

1. Data based on typical application software.

2. Time measured between interrupt event and interrupt vector fetch.

∆t

c(INST) is the number of tCPU cycles needed to finish

the current instruction execution.

3. Data based on design simulation and/or technology characteristics, not tested in production.

Symbol

Parameter

Conditions

Min

Typ 1)

Max

Unit

tc(INST)

Instruction cycle time

tCPU

fCPU=8MHz

250

375

1500

tv(IT)

Interrupt reaction time 2)

tv(IT) = ∆tc(INST) + 10

tCPU

fCPU=8MHz

1.25

2.75

µs

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

VOSC1H

OSC1 input pin high level voltage

see Figure 62

VDD-1

VDD

VOSC1L

OSC1 input pin low level voltage

VSS

VSS+1

tw(OSC1H)

tw(OSC1L)

OSC1 high or low time 3)

tr(OSC1)

tf(OSC1)

OSC1 rise or fall time 3)

OSC1 Input leakage current

VSS≤VIN≤VDD

±1

µA

OSC1

OSC2

fOSC

EXTERNAL

ST72XXX

CLOCK SOURCE

Not connected internally

VOSC1L

VOSC1H

tr(OSC1)

tf(OSC1)

tw(OSC1H)

tw(OSC1L)

90%

10%

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