AT80F51-12AI ATMEL [ATMEL Corporation], AT80F51-12AI Datasheet - Page 3

• Manufacturer Part Number: AT80F51-12AI
• Description: 8-Bit Microcontroller with 4K Bytes QuickFlash Memory
• Manufacturer: ATMEL [ATMEL Corporation]

The AT80F51 provides the following standard features: 4K
bytes of QuickFlash, 128 bytes of RAM, 32 I/O lines, two
16-bit timer/counters, a five vector two-level interrupt archi-
tecture, a full duplex serial port, on-chip oscillator and clock
circuitry. In addition, the AT80F51 is designed with static
logic for operation down to zero frequency and supports
two software selectable power saving modes. The Idle
M o d e s t o p s t h e C P U w h i l e a l l o w i n g t h e R A M ,
timer/counters, serial port and interrupt system to continue
functioning. The Power Down Mode saves the RAM con-
tents but freezes the oscillator disabling all other chip func-
tions until the next hardware reset.
Pin Description
V
Supply voltage.
GND
Ground.
Port 0
Port 0 is an 8-bit open drain bidirectional 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 may also be configured to be the multiplexed low-
order address/data bus during accesses to external pro-
gram and data memory. In this mode P0 has internal pul-
lups.
Port 0 also outputs the code bytes during program verifica-
tion. External pullups are required during program verifica-
tion.
Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pullups.
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 internal pullups 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
QuickFlash verification.
Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pullups.
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 pullups and can be used as inputs. As inputs,
Port 2 pins that are externally 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 it uses strong internal pullups
when emitting 1s. During accesses to external data mem-
CC
IL
IL
) because of the internal pullups.
) because of the internal pullups.
ory 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 QuickFlash verification.
Port 3
Port 3 is an 8-bit bidirectional I/O port with internal pullups.
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 pullups and can be used as inputs. As inputs,
Port 3 pins that are externally being pulled low will source
current (I
Port 3 also serves the functions of various special features
of the AT80F51 as listed below:
Port 3 also receives some control signals for QuickFlash
verification.
RST
Reset input. A high on this pin for two machine cycles while
the oscillator is running resets the device.
ALE
Address Latch Enable output pulse for latching the low byte
of the address during accesses to external memory.
In normal operation ALE is emitted at a constant rate of 1/6
the oscillator frequency, and may be used for external tim-
ing or clocking purposes. Note, however, that one ALE
pulse is skipped during each access to external Data Mem-
ory.
If desired, ALE operation can be disabled by setting bit 0 of
SFR location 8EH. With the bit set, ALE is active only dur-
ing a MOVX or MOVC instruction. Otherwise, the pin is
weakly pulled high. Setting the ALE-disable bit has no
effect if the microcontroller is in external execution mode.
PSEN
Program Store Enable is the read strobe to external pro-
gram memory.
When the AT80F51 is executing code from external pro-
gram memory, PSEN is activated twice each machine
Port Pin
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
IL
) because of the pullups.
Alternate Functions
RXD (serial input port)
INT0 (external interrupt 0)
INT1 (external interrupt 1)
RD (external data memory read strobe)
TXD (serial output port)
T0 (timer 0 external input)
T1 (timer 1 external input)
WR (external data memory write strobe)
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