AT89S52
Serial Port Timing: Shift Register Mode Test Conditions
The values in this table are valid for VCC = 4.0V to 5.5V and Load Capacitance = 80 pF.
12 MHz Osc
Variable Oscillator
Symbol
tXLXL
Parameter
Min
1.0
700
50
Max
Min
12tCLCL
10tCLCL-133
2tCLCL-80
0
Max
Units
µs
Serial Port Clock Cycle Time
tQVXH
tXHQX
tXHDX
tXHDV
Output Data Setup to Clock Rising Edge
Output Data Hold After Clock Rising Edge
Input Data Hold After Clock Rising Edge
Clock Rising Edge to Input Data Valid
ns
ns
0
ns
700
10tCLCL-133
ns
Shift Register Mode Timing Waveforms
INSTRUCTION
ALE
0
1
2
3
4
5
6
7
8
tXLXL
CLOCK
tQVXH
tXHQX
1
WRITE TO SBUF
0
2
3
4
5
6
7
tXHDX
SET TI
tXHDV
OUTPUT DATA
CLEAR RI
VALID
VALID
VALID
VALID
VALID
VALID
VALID
VALID
SET RI
INPUT DATA
AC Testing Input/Output Waveforms(1)
Float Waveforms(1)
+ 0.1V
- 0.1V
+ 0.1V
VCC - 0.5V
VOL
VLOAD
0.2 VCC + 0.9V
Timing Reference
Points
VLOAD
TEST POINTS
- 0.1V
0.2 VCC - 0.1V
0.45V
VLOAD
VOL
Note:
1. For timing purposes, a port pin is no longer floating
when a 100 mV change from load voltage occurs. A
port pin begins to float when a 100 mV change from
the loaded VOH/VOL level occurs.
Note:
1. AC Inputs during testing are driven at VCC - 0.5V
for a logic 1 and 0.45V for a logic 0. Timing mea-
surements are made at VIH min. for a logic 1 and VIL
max. for a logic 0.
27
ATMEL [ ATMEL ]
