AT89C55WD Atmel Corporation, AT89C55WD Datasheet - Page 28

• Manufacturer Part Number: AT89C55WD
• Manufacturer: Atmel Corporation

Specifications of AT89C55WD

• Flash (kbytes): 20 Kbytes
• Max. Operating Frequency: 24 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Uart: 1
• Sram (kbytes): 0.25
• Operating Voltage (vcc): 4.0 to 6.0
• Timers: 3
• Watchdog: Yes

29. External Program Memory Read Cycle
30. External Data Memory Read Cycle
28
AT89C55WD
PORT 0
PORT 2
PORT 0
PORT 2
PSEN
PSEN
ALE
ALE
RD
A0 - A7 FROM RI OR DPL
t
LHLL
t
AVLL
t
AVLL
t
P2.0 - P2.7 OR A8 - A15 FROM DPH
LHLL
t
AVWL
t
LLAX
t
A0 - A7
AVDV
t
LLAX
t
LLWL
t
t
LLPL
RLAZ
t
t
LLDV
AVIV
A8 - A15
t
PLAZ
t
RLRH
t
RLDV
DATA IN
t
t
LLIV
PLIV
INSTR IN
t
PXIX
t
PXIZ
t
t
t
A0 - A7 FROM PCL
RHDZ
t
PLPH
PXAV
t
RHDX
WHLH
A8 - A15 FROM PCH
A8 - A15
A0 - A7
INSTR IN
1921D–MICRO–6/08