Rainbow Electronics AT89C51SND1C - Manual (Page 200)

200
AT8xC51SND1C
4109E–8051–06/03
Figure 158. AC Testing Input/Output Waveforms
Note: 1. During AC testing, all inputs are driven at V
DD
-0.5 V for a logic 1 and 0.45 V for a
logic 0.
2. Timing measurements are made on all outputs at V
IH
min for a logic 1 and V
IL
max for
a logic 0.
Figure 159. Float Waveforms
Note: For timing purposes, a 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 loading V
OH
/V
OL
level
occurs with I
OL
/I
OH
= ± 20 mA.
0.45 V
V
DD
- 0.5
0.7 V
DD
0.3 V
DD
V
IH
min
V
IL
max
INPUTS OUTPUTS
V
LOAD
V
OH
- 0.1 V
V
OL
+ 0.1 V
V
LOAD
+ 0.1 V
V
LOAD
- 0.1 V
Timing Reference Points