SMSC COM20020 manual NON-MULTIPLEXED BUS, 68XX-LIKE Control Signals Read Cycle

A0-A2

t1

VALID

t2

nCS

t4

DIR

t3

t7

t5

t6

nDS

t8

t9

D0-D7

VALID DATA

Parameter

min

max

units

t1

Address Setup to nDS Active

15

nS

t2

Address Hold from nDS Inactive

10

nS

t3

nCS Setup to DS Active

5**

nS

t4

nCS Hold from DS Inactive

0

nS

t5

DIR Setup to nDS Active

10

nS

t6

Cycle Time (nDS Low to Next Time Low)

4T*

nS

t7

DIR Hold from nDS Active

10

nS

t8

nDS Low to Valid Data

40

nS

t9

nDS High to Data High Impedence

0

20

nS

*T is the Arbitration Clock Period.

T is identical to XTAL1 if SLOW ARB = 0, T is twice XTAL1 period if SLOW ARB = 1

**nCS may become active after control becomes active, but the access time will now be 45nS measured from the leading edge of nCS.

Note 1: The Microcontroller typically accesses the COM20020 on every other cycle. Therefore, the cycle time specified in the microcontroller's datasheet should be doubled when considering back-to-back COM20020 cycles.

FIGURE 12A - NON-MULTIPLEXED BUS, 68XX-LIKE CONTROL SIGNALS; READ CYCLE

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