MOTOROLA
MC68306 USER'S MANUAL
3- 35
On the rising edge of the clock, at the end of S7 (which may be the start of
S0 for the next bus cycle), the processor places the address bus in the
high-impedance state. During a write cycle, the processor also places the
data bus in the high-impedance state and drives R/
W
high. External logic
circuitry should respond to the negation of the
AS
and
UDS
/
LDS
by negating
DTACK
and/or
BERR
. Parameter #28 is the hold time for
DTACK
, and
parameter #30 is the hold time for
BERR
.
Figure 3-32 shows a synchronous read cycle and the important timing parameters that
apply. The timing for a synchronous read cycle, including relevant timing parameters, is
shown in Figure 3-33.
ADDR
UDS/LDS
R/W
AS
CLOCK
DTACK
6
9
S0
S1
S2
S3
S4
S5
S6
S7
S0
18
47
27
DATA
Figure 3-32. Synchronous Read Cycle