
116
AT89C51RB2/RC2
4180E–8051–10/06
External Data Memory Read Cycle
Serial Port Timing - Shift
Register Mode
Table 80. Symbol Description
Table 81. AC Parameters for a Fix Clock
Table 82. AC Parameters for a Variable Clock
ALE
PSEN
RD
PORT 0
PORT 2
A0-A7
DATA IN
ADDRESS
OR SFR-P2
TAVWL
TLLWL
TRLAZ
ADDRESS A8-A15 OR SFR P2
TRHDZ
TWHLH
TRLRH
TLLDV
TRHDX
TLLAX
TAVDV
Symbol
Parameter
T
XLXL
Serial port clock cycle time
T
QVHX
Output data set-up to clock rising edge
T
XHQX
Output data hold after clock rising edge
T
XHDX
Input data hold after clock rising edge
T
XHDV
Clock rising edge to input data valid
Symbol
-M
-L
Units
Min
Max
Min
Max
TXLXL
300
ns
TQVHX
200
ns
T
XHQX
30
ns
T
XHDX
00
ns
T
XHDV
117
ns
Symbol
Type
Standard
Clock
X2 Clock
X Parameter for -
M Range
X Parameter for -L
Range
Units
TXLXL
Min
12 T
6 T
ns
TQVHX
Min
10 T - x
5 T - x
50
ns
TXHQX
Min
2 T - x
T - x
20
ns
TXHDX
Min
x
0
ns
TXHDV
Max
10 T - x
5 T- x
133
ns