AC Switching Characteristics
READ TIMING DATA FROM PERIPHERAL TO MICROPROCESSOR
V
DD
e
5V
g
0 5V C
L
e
100 pF
Commercial
Specification
T
A
e b
40 C to
a
85 C
Min
t
AD
t
CSD
t
RD
t
RW
t
RA
t
CSH
t
RH
t
HZ
Address Bus Valid to Data Valid
Chip Select On to Data Valid
Read Strobe On to Data Valid
Read Strobe Width (Note 3 Note 7)
Address Bus Hold Time from Trailing Edge
of Read Strobe
Chip Select Hold Time from Trailing Edge
of Read Strobe
Data Hold Time from Trailing Edge
of Read Strobe
Time from Trailing Edge of Read Strobe
Until O P Drivers are TRI-STATE
0
0
70
160
250
Typ
390
140
140
Max
650
300
300
DC
ns
ns
ns
ns
ns
ns
ns
Symbol
Parameter
Units
WRITE TIMING DATA FROM MICROPROCESSOR TO PERIPHERAL
V
DD
e
5V
g
0 5V
Commercial
Specification
T
A
e b
40 C to
a
85 C
Min
t
AW
t
CSW
t
DW
t
WW
t
WCS
t
WA
t
WD
t
AWS
Address Bus Valid to Write Strobe
O
(Note 4 Note 6)
Chip Select On to Write Strobe
O
Data Bus Valid to Write Strobe
O
Write Strobe Width (Note 6)
Chip Select Hold Time Following
Write Strobe
O
Address Bus Hold Time Following
Write Strobe
O
Data Bus Hold Time Following
Write Strobe
O
Address Bus Valid Before
Start of Write Strobe
400
250
400
250
0
0
100
70
35
20
Typ
125
100
220
95
Max
ns
ns
ns
ns
ns
ns
ns
ns
Symbol
Parameter
Units
Note 3
Except for special case restriction with interrupts programmed max read strobe width of control register (ADDR 0) is 30 ms See section on Interrupt
Programming
Note 4
All timings measured to the trailing edge of write strobe (data latched by the trailing edge of WR)
Note 5
Input test waveform peak voltages are 2 4V and 0 4V Output signals are measured to their 2 4V and 0 4V levels
Note 6
Write strobe as used in the Write Timing Table is defined as the period when both chip select and write inputs are low ie WS
e
CS
a
WR Hence write
strobe commences when both signals are low and terminates when the first signal returns high
Note 7
Read strobe as used in the Read Timing Table is defined as the period when both chip select and read inputs are low ie RS
e
CS
a
RD
Note 8
Typical numbers are at V
CC
e
5 0V and T
A
e
25 C
3
NSC [ NATIONAL SEMICONDUCTOR ]
