Datasheet

19
1921D–MICRO–6/08
AT89C55WD
Figure 18-1. Oscillator Connections
Note: C1, C2 = 30 pF ± 10 pF for Crystals
= 40 pF ± 10 pF for Ceramic Resonators
Figure 18-2. External Clock Drive Configuration
Table 18-1. Status of External Pins During Idle and Power-down Modes
Mode
Program
Memory ALE PSEN PORT0 PORT1 PORT2 PORT3
Idle Internal 1 1 Data Data Data Data
Idle External 1 1 Float Data Address Data
Power-down Internal 0 0 Data Data Data Data
Power-down External 0 0 Float Data Data Data
C2
XTAL2
GND
XTAL1
C1
XTAL2
XTAL1
GND
NC
EXTERNAL
OSCILLATOR
SIGNAL