AC Characteristics
(Under Operating Conditions; Load Capacitance for Port 0, ALE/PROG, and PSEN = 100 pF; Load Capacitance for all other
outputs = 80 pF)
External Program and Data Memory Characteristics
Symbol
Parameter
12 MHz Oscillator
16 to 24 MHz Oscillator
Units
Min
Max
Min
0
Max
1/tCLCL
tLHLL
tAVLL
tLLAX
tLLIV
Oscillator Frequency
24
MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ALE Pulse Width
127
43
2tCLCL-40
tCLCL-13
tCLCL-20
Address Valid to ALE Low
Address Hold After ALE Low
ALE Low to Valid Instruction In
ALE Low to PSEN Low
PSEN Pulse Width
48
233
4tCLCL-65
tLLPL
43
tCLCL-13
tPLPH
tPLIV
205
3tCLCL-20
PSEN Low to Valid Instruction In
Input Instruction Hold After PSEN
Input Instruction Float After PSEN
PSEN to Address Valid
Address to Valid Instruction In
PSEN Low to Address Float
RD Pulse Width
145
59
3tCLCL-45
tCLCL-10
tPXIX
0
0
tPXIZ
tPXAV
tAVIV
75
tCLCL-8
312
10
5tCLCL-55
10
tPLAZ
tRLRH
tWLWH
tRLDV
tRHDX
tRHDZ
tLLDV
tAVDV
tLLWL
tAVWL
tQVWX
tQVWH
tWHQX
tRLAZ
tWHLH
400
400
6tCLCL-100
6tCLCL-100
WR Pulse Width
RD Low to Valid Data In
Data Hold After RD
252
5tCLCL-90
0
0
Data Float After RD
97
2tCLCL-28
8tCLCL-150
9tCLCL-165
3tCLCL+50
ALE Low to Valid Data In
Address to Valid Data In
ALE Low to RD or WR Low
Address to RD or WR Low
Data Valid to WR Transition
Data Valid to WR High
517
585
300
200
203
23
3tCLCL-50
4tCLCL-75
tCLCL-20
433
33
7tCLCL-120
tCLCL-20
Data Hold After WR
RD Low to Address Float
RD or WR High to ALE High
0
0
43
123
tCLCL-20
tCLCL+25
AT89C51
4-38
ATMEL [ ATMEL ]
