COM20020-5 Datasheet, PDF (48/58 Pages) SMSC Corporation – Universal Local Area Network Controller with 2K x 8 On-Board RAM

A0-A2
nCS
nRD
D0-D7
VALID
t1
t2
t3
t6
t4
t5
t7
VALID DATA
Parameter
min
max units
t1 Address Setup to nRD Active
t2 Address Hold from nRD Inactive
t3 nCS Setup to nRD Active
t4 nCS Hold from nRD Inactive
t5 _{Cycle Time (nRD Low to Next Time Low)}
t6 _{nRD Low to Valid Data}
t7 _{nRD High to Data High Impedance}
15
nS
10
nS
5**
nS
0
4T*
nS
nS
40
nS
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 COM20020-5 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20020-5 cycles.
FIGURE 12 - NON-MULTIPLEXED BUS, 80XX-LIKE CONTROL SIGNALS; READ CYCLE
48