D.2 Pin States at Reset
Reset in T1 State: Figure D-1 is a timing diagram for the case in which
RES
goes low during the
T1 state of an external memory access cycle. As soon as
RES
goes low, all ports are initialized to
the input state.
AS
,
RD
,
HWR
, and
LWR
go high, and the data bus goes to the high-impedance
state. The address bus is initialized to the low output level 0.5 state after the low level of
RES
is
sampled. Sampling of
RES
takes place at the fall of the system clock (ø).
Figure D-1 Reset during Memory Access (Reset during T1 State)
Access to external address
ø
Address bus
CS
0
AS
RD (read access)
HWR, LWR
Data bus
I/O port
RES
(write access)
(write access)
H'000000
High impedance
High impedance
High impedance
High
High
High
Internal
reset signal
T1
T2
T3
CS
7
to CS
1
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