Features
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Compatible with MCS-51™ Products
4K Bytes of Factory Programmable QuickFlash
™
Memory
Fully Static Operation: 0 Hz to 20 MHz
Three-Level Program Memory Lock
128 x 8-Bit Internal RAM
32 Programmable I/O Lines
Two 16-Bit Timer/Counters
Six Interrupt Sources
Programmable Serial Channel
Low Power Idle and Power Down Modes
Description
The AT80F51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K
bytes of QuickFlash Memory. The device is manufactured using Atmel’s high density
nonvolatile memory technology and is compatible with the industry standard MCS-
51™ instruction set and pinout. The on-chip QuickFlash allows custom codes to be
quickly programmed in the factory. By combining a versatile 8-bit CPU with Quick-
Flash on a monolithic chip, the Atmel AT80F51 is a powerful microcomputer which
provides a highly flexible and cost effective solution to many embedded control appli-
cations.
(continued)
8-Bit
Microcontroller
with 4K Bytes
QuickFlash
™
Memory
AT80F51
Pin Configurations
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RST
(RXD) P3.0
(TXD) P3.1
(INT0) P3.2
(INT1) P3.3
(T0) P3.4
(T1) P3.5
(WR) P3.6
(RD) P3.7
X TA L 2
X TA L 1
GND
PDIP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
VCC
P0.0 (AD0)
P0.1 (AD1)
P0.2 (AD2)
P0.3 (AD3)
P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)
EA
ALE
PSEN
P2.7 (A15)
P2.6 (A14)
P2.5 (A13)
P2.4 (A12)
P2.3 (A11)
P2.2 (A10)
P2.1 (A9)
P2.0 (A8)
TQFP
(AD0)
(AD1)
(AD2)
(AD3)
44 42 40
38
36 34
43 41 39
37
35
P1.5
P1.6
P1.7
RST
P3.0
NC
P3.1
P3.2
P3.3
P3.4
P3.5
P1.4
P1.3
P1.2
P1.1
P1.0
NC
VCC
P0.0
P0.1
P0.2
P0.3
INDEX
CORNER
(RXD)
(TXD)
(INT0)
(INT1)
(T0)
(T1)
1
2
3
4
5
6
7
8
9
10
11
13 15 17 19 21
12 14 16 18 20 22
(WR) P3.6
(RD) P3.7
X TA L 2
X TA L 1
GND
GND
(A8) P2.0
(A9) P2.1
(A10) P2.2
(A11) P2.3
(A12) P2.4
33
32
31
30
29
28
27
26
25
24
23
P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)
EA
NC
ALE
PSEN
P2.7 (A15)
P2.6 (A14)
P2.5 (A13)
PLCC
(AD0)
(AD1)
(AD2)
(AD3)
(RXD)
(TXD)
(INT0)
(INT1)
(T0)
(T1)
P1.5
P1.6
P1.7
RST
P3.0
NC
P3.1
P3.2
P3.3
P3.4
P3.5
6
4
2
44 42 40
1
3
4 3 4 13 9
7 5
8
38
9
37
10
36
11
35
12
34
13
33
14
32
15
31
16
30
1 7 1 9 2 1 2 3 2 5 2 72 9
18 20 22 24 26 28
(WR) P3.6
(RD) P3.7
X TA L 2
X TA L 1
GND
NC
(A8) P2.0
(A9) P2.1
(A10) P2.2
(A11) P2.3
(A12) P2.4
P1.4
P1.3
P1.2
P1.1
P1.0
NC
VCC
P0.0
P0.1
P0.2
P0.3
INDEX
CORNER
P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)
EA
NC
ALE
PSEN
P2.7 (A15)
P2.6 (A14)
P2.5 (A13)
0979A-A–12/97
3-3
Block Diagram
P0.0 - P0.7
P2.0 - P2.7
V
CC
PORT 0 DRIVERS
GND
PORT 2 DRIVERS
RAM ADDR.
REGISTER
RAM
PORT 0
LATCH
PORT 2
LATCH
QUICK
FLASH
B
REGISTER
ACC
STACK
POINTER
PROGRAM
ADDRESS
REGISTER
TMP2
TMP1
BUFFER
ALU
INTERRUPT, SERIAL PORT,
AND TIMER BLOCKS
PC
INCREMENTER
PSW
PROGRAM
COUNTER
PSEN
ALE
EA
RST
PORT 1
LATCH
PORT 3
LATCH
TIMING
AND
CONTROL
INSTRUCTION
REGISTER
DPTR
OSC
PORT 1 DRIVERS
PORT 3 DRIVERS
P1.0 - P1.7
P3.0 - P3.7
3-4
AT80F51
AT80F51
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
Mode stops the CPU while allowing the RAM,
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.
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
IL
) because of the pullups.
Port 3 also serves the functions of various special features
of the AT80F51 as listed below:
Port Pin
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
Alternate Functions
RXD (serial input port)
TXD (serial output port)
INT0 (external interrupt 0)
INT1 (external interrupt 1)
T0 (timer 0 external input)
T1 (timer 1 external input)
WR (external data memory write strobe)
RD (external data memory read strobe)
Pin Description
V
CC
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
IL
) because of the internal pullups.
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
IL
) because of the internal pullups.
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-
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
3-5
cycle, except that two PSEN activations are skipped during
each access to external data memory.
EA
External Access Enable. EA must be strapped to GND in
order to enable the device to fetch code from external pro-
gram memory locations starting at 0000H up to FFFFH.
Note, however, that if lock bit 1 is programmed, EA will be
internally latched on reset.
EA should be strapped to V
CC
for internal program execu-
tions.
XTAL1
Input to the inverting oscillator amplifier and input to the
internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier.
an unexpected write to a port pin when Idle is terminated by
reset, the instruction following the one that invokes Idle
should not be one that writes to a port pin or to external
memory.
Figure 1.
Oscillator Connections
C2
XTAL2
C1
XTAL1
GND
Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively,
of an inverting amplifier which can be configured for use as
an on-chip oscillator, as shown in Figure 1. Either a quartz
crystal or ceramic resonator may be used. To drive the
device from an external clock source, XTAL2 should be left
unconnected while XTAL1 is driven as shown in Figure 2.
There are no requirements on the duty cycle of the external
clock signal, since the input to the internal clocking circuitry
is through a divide-by-two flip-flop, but minimum and maxi-
mum voltage high and low time specifications must be
observed.
Note:
C1, C2 = 30 pF
±
10 pF for Crystals
= 40 pF
±
10 pF for Ceramic Resonators
Figure 2.
External Clock Drive Configuration
Idle Mode
In idle mode, the CPU puts itself to sleep while all the on-
chip peripherals remain active. The mode is invoked by
software. The content of the on-chip RAM and all the spe-
cial functions registers remain unchanged during this
mode. The idle mode can be terminated by any enabled
interrupt or by a hardware reset.
It should be noted that when idle is terminated by a hard
ware reset, the device normally resumes program execu-
tion, from where it left off, up to two machine cycles before
the internal reset algorithm takes control. On-chip hardware
inhibits access to internal RAM in this event, but access to
the port pins is not inhibited. To eliminate the possibility of
Power Down Mode
In the power down mode the oscillator is stopped, and the
instruction that invokes power down is the last instruction
executed. The on-chip RAM and Special Function Regis-
ters retain their values until the power down mode is termi-
Status of External Pins During Idle and Power Down Modes
Mode
Idle
Idle
Power Down
Power Down
Program Memory
Internal
External
Internal
External
ALE
1
1
0
0
PSEN
1
1
0
0
PORT0
Data
Float
Data
Float
PORT1
Data
Data
Data
Data
PORT2
Data
Address
Data
Data
PORT3
Data
Data
Data
Data
3-6
AT80F51
AT80F51
nated. The only exit from power down is a hardware reset.
Reset redefines the SFRs but does not change the on-chip
RAM. The reset should not be activated before V
CC
is
restored to its normal operating level and must be held
active long enough to allow the oscillator to restart and sta-
bilize.
When lock bit 1 is programmed, the logic level at the EA pin
is sampled and latched during reset. If the device is pow-
ered up without a reset, the latch initializes to a random
value, and holds that value until reset is activated. It is nec-
essary that the latched value of EA be in agreement with
the current logic level at that pin in order for the device to
function properly.
Program Memory Lock Bits
On the chip are three lock bits which can be left unpro-
grammed (U) or can be programmed (P) to obtain the addi-
tional features listed in the table below:
Lock Bit Protection Modes
Program Lock Bits
LB1
1
2
U
P
LB2
U
U
LB3
U
U
No program lock features.
MOVC instructions executed from external program memory are disabled from fetching code
bytes from internal memory, EA is sampled and latched on reset, and further programming of the
QuickFlash is disabled.
Same as mode 2, also verify is disabled.
Same as mode 3, also external execution is disabled.
Protection Type
3
4
P
P
P
P
U
P
Programming/Verifying the QuickFlash
The AT80F51 can only be programmed by Atmel. Cus-
tomer codes should be submitted in
duplicate
on a floppy
disk or uploaded to Atmel’s bulletin board or Web site. The
code should be in the Intel Hex format. The desired states
of the Lock Bits should be specified. Once programmed,
the code memory and Lock Bits cannot be erased or repro-
grammed.
Please consult the factory or Atmel’s representatives for
details on submitting custom codes.
Program Verify:
If lock bits LB1 and LB2 have not been
programmed, the programmed code data can be read back
via the address and data lines for verification. The lock bits
cannot be verified directly. Verification of the lock bits is
achieved by observing that their features are enabled.
Reading the Signature Bytes:
The signature bytes are
read by the same procedure as a normal verification of
locations 030H, 031H, and 032H, except that P3.6 and
P3.7 must be pulled to a logic low. The values returned are
as follows.
(030H) = 1EH indicates manufactured by Atmel
(031H) = 80H indicates QuickFlash
(032H) = 01H indicates AT80F51
QuickFlash Verification Modes
Mode
Read Code Data
Read Signature Byte
RST
H
H
PSEN
L
L
ALE
H
H
EA
H
H
P2.6
L
L
P2.7
L
L
P3.6
H
L
P3.7
H
L
3-7
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