at89s51-33sc ATMEL Corporation, at89s51-33sc Datasheet - Page 4

• Manufacturer Part Number: at89s51-33sc
• Description: At89s51, 8-bit Microcontroller With 4k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

4. Pin Description
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4
VCC
GND
VDD
PWRVDD
PWRGND
Port 0
Port 1
AT89S51
Supply voltage (all packages except 42-PDIP).
Ground (all packages except 42-PDIP; for 42-PDIP GND connects only the logic core and the
embedded program memory).
Supply voltage for the 42-PDIP which connects only the logic core and the embedded program
memory.
Supply voltage for the 42-PDIP which connects only the I/O Pad Drivers. The application board
MUST connect both VDD and PWRVDD to the board supply voltage.
Ground for the 42-PDIP which connects only the I/O Pad Drivers. PWRGND and GND are
weakly connected through the common silicon substrate, but not through any metal link. The
application board MUST connect both GND and PWRGND to the board ground.
Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink eight TTL
inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs.
Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses
to external program and data memory. In this mode, P0 has internal pull-ups.
Port 0 also receives the code bytes during Flash programming and outputs the code bytes dur-
ing program verification. External pull-ups are required during program verification.
Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can
sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the inter-
nal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low
will source current (I
Port 1 also receives the low-order address bytes during Flash programming and verification.
Port Pin
P1.5
P1.6
P1.7
IL
) because of the internal pull-ups.
Alternate Functions
MOSI (used for In-System Programming)
MISO (used for In-System Programming)
SCK (used for In-System Programming)
2487C–MICRO–03/05