SMSC COM20020 manual Multiplexed BUS, 80XX-LIKE Control Signals Read Cycle

AD0-AD2,

D3-D7

VALID

t1 t2,

t4

nCS

t3

ALE

nRD t5

t6

VALID DATA

t7

t8

	Parameter	min	max	units
t1	Address Setup to ALE Low	30		nS
t2	Address Hold from ALE Low	10		nS
t3	nCS Setup to ALE Low	10		nS
t4	nCS Hold from ALE Low	20		nS
t5	ALE Low to nRD Low	15	40	nS
t6	nRD Low to Valid Data			nS
t7	nRD High to Data High Impedance	0	20	nS
t8	Cycle Time (nRD Low to Next Time Low)	4T*		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

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 10A - MULTIPLEXED BUS, 80XX-LIKE CONTROL SIGNALS; READ CYCLE

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