AT89S8252-16JA ATMEL [ATMEL Corporation], AT89S8252-16JA Datasheet - Page 4

• Manufacturer Part Number: AT89S8252-16JA
• Description: 8-Bit Microcontroller with 8K Bytes Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Port 2
Port 3
4
AT89S8252
Some Port 1 pins provide additional functions. P1.0 and P1.1 can be configured to be
the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger input
(P1.1/T2EX), respectively.
Furthermore, P1.4, P1.5, P1.6, and P1.7 can be configured as the SPI slave port select,
data input/output and shift clock input/output pins as shown in the following table.
Port 1 also receives the low-order address bytes during Flash programming and
verification.
Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers
can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are exter-
nally being pulled low will source current (I
Port 2 emits the high-order address byte during fetches from external program memory
and during accesses to external data memory that use 16-bit addresses (MOVX @
DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During
accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits
the contents of the P2 Special Function Register.
Port 2 also receives the high-order address bits and some control signals during Flash
programming and verification.
Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers
can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are exter-
nally being pulled low will source current (I
Port 3 receives some control signals for Flash programming and verification.
Port 3 also serves the functions of various special features of the AT89S8252, as shown
in the following table.
Port Pin
P1.0
P1.1
P1.4
P1.5
P1.6
P1.7
Alternate Functions
T2EX (Timer/Counter 2 capture/reload trigger and direction control)
SS (Slave port select input)
MISO (Master data input, slave data output pin for SPI channel)
T2 (external count input to Timer/Counter 2), clock-out
MOSI (Master data output, slave data input pin for SPI channel)
SCK (Master clock output, slave clock input pin for SPI channel)
IL
IL
) because of the internal pull-ups.
) because of the pull-ups.
0401F–MICRO–11/03