COM20019IP datasheet(59/81 Pages) SMSC

59 / 81 page

FIGURE 12 - MULTIPLEXED BUS, 68XX-LIKE CONTROL SIGNALS; WRITE CYCLE

DISCONTINUED DATASHEET

AD0-AD2,

VALID

VALID DATA

nCS

ALE

t2,

D3-D7

Note 2

t8**

nWR

t10

nRD

t13

t11

t12

Note 3

Parameter

min

max

units

t10

t11

t12

t13

4TARB

Address Setup to ALE Low

Address Hold from ALE Low

nCS Setup to ALE Low

nCS Hold from ALE Low

ALE Low to nDS Low

Valid Data Setup to nDS High

Data Hold from nDS High

ALE High Width

ALE Low Width

nWR Low Width

nWR High Width

nRD

to nWR Low

Cycle Time (nWR

to Next

)**

TARB is the Arbitration Clock Period

TARB is identical to Topr if SLOW ARB = 0

TARB is twice Topr if SLOW ARB = 1

Topr is the period of operation clock. Same as the XTAL1 period.

The Microcontroller typically accesses the COM20019 on every other cycle.

Therefore, the cycle time specified in the microcontroller's datasheet

should be doubled when considering back-to-back COM20019 cycles.

Note 1:

Any cycle occurring after a write to Address Pointer Low Register requires a

minimum of 4TARB from the trailing edge of nWR to the leading edge of the

next nWR.

Note 2:

Write cycle for Address Pointer Low Register occurring after a write to Data

leading edge of the next nWR.

Note 3:

Write cycle for Address Pointer Low Register occurring after a read from Data

the trailing edge of nRD to the

leading edge of nWR.

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COM20019IP датащи(PDF) 59 Page - SMSC Corporation

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