external clock drive characteristics (xtal1), external clock drive waveforms, ac testing input/output waveforms – Rainbow Electronics T89C51RD2 User Manual
Page 84: float waveforms, External clock drive characteristics (xtal1), Float waveforms
Rev. F - 15 February, 2001
84
T89C51RD2
9.5.11. External Clock Drive Characteristics (XTAL1)
Table 48. AC Parameters
9.5.12. External Clock Drive Waveforms
9.5.13. AC Testing Input/Output Waveforms
AC inputs during testing are driven at V
CC
- 0.5 for a logic “1” and 0.45V for a logic “0”. Timing measurement
are made at V
IH
min for a logic “1” and V
IL
max for a logic “0”.
9.5.14. Float Waveforms
For timing purposes as port pin is no longer floating when a 100 mV change from load voltage occurs and begins
to float when a 100 mV change from the loaded V
OH
/V
OL
level occurs. I
OL
/I
OH
≥ ±
20mA.
Symbol
Parameter
Min
Max
Units
T
CLCL
Oscillator Period
25
ns
T
CHCX
High Time
5
ns
T
CLCX
Low Time
5
ns
T
CLCH
Rise Time
5
ns
T
CHCL
Fall Time
5
ns
T
CHCX
/T
CLCX
Cyclic ratio in X2 mode
40
60
%
V
CC
-0.5V
0.45V
0.7V
CC
0.2V
CC
-0.1
T
CHCL
T
CLCX
T
CLCL
T
CLCH
T
CHCX
INPUT/OUTPUT
0.2 V
CC
+ 0.9
0.2 V
CC
- 0.1
V
CC
-0.5 V
0.45 V
FLOAT
V
OH
- 0.1 V
V
OL
+ 0.1 V
V
LOAD
V
LOAD
+ 0.1 V
V
LOAD
- 0.1 V