At8xc51snd1c – Rainbow Electronics AT89C51SND1C User Manual
Page 200
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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
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