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49
AD0-AD2,
VALID
nCS
t1
t3
t8
T is the Arbitration Clock Period.
T is identical to XTAL1 if SLOW ARB = 0,
*
T is twice XTAL1 period if SLOW ARB = 1
ALE
VALID DATA
t2,
t6
t5
t4
t7
D3-D7
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.
Parameter
min
max units
t1
t2
t3
t4
t5
t6
t7
t8
30
10
10
20
15
10
4T*
nS
nS
nS
nS
nS
nS
nS
nS
Address Setup to ALE Low
Address Hold from ALE Low
nCS Setup to ALE Low
nCS Hold from ALE Low
ALE Low to nWR Low
Valid Data Setup to nWR High
Data Hold from nWR High
Cycle Time (nWR Low to Next Time Low)**
30
Note 2
t8**
Note 1:
Any cycle occurring after a write to Address Pointer Low Register requires a
minimum of 4T from the trailing edge of nWR to the leading edge of the
next nWR.
Note 2:
**
nWR
FIGURE 11A - MULTIPLEXED BUS, 80XX-LIKE CONTROL SIGNALS; WRITE CYCLE