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

A0-A2		VALID
	t1		t2
nCS
			t4
DIR	t3
	t5	t6	t7
nDS
			Note 2
		t8	t6**
			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 nDS Active	5		nS
t4	nCS Hold from nDS 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 Inactive	10		nS
t8	Valid Data Setup to nDS High	30**		nS
t9	Data Hold from nDS High	10		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 data setup time will now be 30 nS measured from the later of nCS falling or Valid Data available.

Note 1:

Note 2:

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.

Any cycle occurring after a write to the Address Pointer Low Register requires a minimum of 4T from the trailing edge of nDS to the leading edge of the next nDS.

FIGURE 13A - NON-MULTIPLEXED BUS, 68XX-LIKE CONTROL SIGNALS; WRITE CYCLE

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