Typewriter User Manual

10-6 MC68340 USER’S MANUAL MOTOROLA
S0
S1
S2
SW
SW
SW
SW
S3
S4
S5
S0
S1
S2
CLKOUT
CS0
Q1
DSACK0
Figure 10-9. 8-bit Boot ROM Timing
10.2.2 Access Time Calculations
The two time paths that are critical in an MC68340 application using the CS≈ signals are
shown in Figure 10-10. The first path is the time from address valid to when data must be
available to the processor; the second path is the time from
CS≈ asserted to when data
must be available to the processor.
CS
D15–D0
A31–A0
CLKOUT
S0
S4
S1
S5
S0
t
27
t
CSDV
t
t
6
AD
V
t
9
Figure 10-10. Access Time Computation Diagram
As shown in the diagram, an equation for the address access time, t
ADV
, can be
developed as follows:
t
ADV
= t
cyc
(N
c
– 0.5) – t
s9
– t
s27
where:
t
cyc
= system CLKOUT period
N
c
= number of clocks per bus cycle
t
s6
= CLKOUT high to address valid = 30 ns maximum at 16.78 MHz
t
s27
= data-in valid to CLKOUT low setup = 5 ns minimum at 16.78 MHz
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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