ATMEL AT89C52-16JC, AT89C52-16JA, AT89C52-16AI, AT89C52-16AC, AT89C52-16AA Datasheet

Features

Compatible with MCS-51™ Products

•

8K Bytes of In-System Reprogrammable Flash Memory

•

– Endurance: 1,000 Write/Erase Cycles

Fully Static Operation: 0 Hz to 24 MHz

•

Three-Level Program Memory Lock

•

256 x 8-Bit Internal RAM

•

32 Programmable I/O Lines

•

Three 16-Bit Timer/Counters

•

Eight Interrupt Sources

•

Programmable Serial Channel

•

Low Power Idle and Power Down Modes

•

Description

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K
bytes of Flash progr ammab le and era sable read only memory ( PERO M). The devi ce
is manufactured using Atmel’s high density nonvolatile memory technology and is
compatible with th e industry standard 8 0C51 and 8 0C52 instr uction se t and pino ut.
The on-chip Flash allows the program memory to be reprogrammed in-system or by a
conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU
with Flash on a mono lithic chip, th e Atmel AT89C5 2 is a powerful microcompute r
which provides a hi gh ly flex ib le and c os t e ffec ti ve s olu tio n to m any e mbe dde d c on tro l
applications.

Pin Configurations

PQFP/TQFP

INDEX
CORNER

P1.5
P1.6
P1.7

RST

(RXD) P3.0

NC

(TXD) P3.1
(INT0) P3.2
(INT1) P3.3

(T0) P3.4
(T1) P3.5

P1.4

44

1
2
3
4
5
6
7
8
9
10
11

13

12

(WR) P3.6

P1.3

P1.2

424340

41

15

14

XTAL2

(RD) P3.7

P1.1 (T2 EX)

16

XTAL1

P1.0 (T2)

39

17

GND

NC

38

18

GND

VCC

37

19

(A8) P2.0

P0.1 (AD1)

P0.0 (AD0)

36

35

21

20

(A9) P2.1

(A10) P2.2

P0.2 (AD2)

P0.3 (AD3)

34

33
32

31
30
29
28
27
26
25
24
23

22

(A11) P2.3

(A12) P2.4

P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)

EA/VPP

NC

ALE/PROG
PSEN

P2.7 (A15)
P2.6 (A14)
P2.5 (A13)

PDIP

(T2) P1.0

(T2 EX) P1.1

(RXD) P3.0

(TXD) P3.1
(INT0) P3.2
(INT1) P3.3

(T0) P3.4
(T1) P3.5

(WR) P3.6

(RD) P3.7 P2.3 (A11)

XTAL2 P2.2 (A10)
XTAL1 P2.1 (A9)

1
2

P1.2

3

P1.3

4

P1.4

5

P1.5

6
7

P1.6
P1.7

8

RST

9
10
11
12
13
14
15
16
17
18
19

GND P2.0 (A8)

20

68PLCC

INDEX
CORNER

P1.5
P1.6
P1.7

RST

(RXD) P3.0

NC

(TXD) P3.1
(INT0) P3.2
(INT1) P3.3

(T0) P3.4
(T1) P3.5

P1.2

P1.1 (T2 EX)

P1.3

P1.4

65444

2

3

7
8
9
10
11
12
13
14
15
16
17 29

21

181920 24

22

XTAL2

XTAL1

(RD) P3.7

(WR) P3.6

P1.0 (T2)

1

23

GND

NC

NC

(continued)

V

CC

40

P0.0 (AD0)

39
38

P0.1 (AD1)

37

P0.2 (AD2)

36

P0.3 (AD3)

35

P0.4 (AD4)

34

P0.5 (AD5)
P0.6 (AD6)

33

P0.7 (AD7)

32

EA/VPP

31

ALE/PROG

30

PSEN

29

P2.7 (A15)

28

P2.6 (A14)

27

P2.5 (A13)

26

P2.4 (A12)

25
24
23
22
21

VCC

P0.0 (AD0)

P0.2 (AD2)

P0.3 (AD3)

P0.1 (AD1)

424340

41

39

38
37

36
35
34
33
32
31
30

252827

26

(A9) P2.1

(A8) P2.0

(A10) P2.2

(A12) P2.4

(A11) P2.3

P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)

EA/VPP

NC

ALE/PROG
PSEN

P2.7 (A15)
P2.6 (A14)
P2.5 (A13)

8-Bit
Microcontroller
with 8K Bytes
Flash

AT89C52

0313F-A–12/97

4-61

Block Diagram

V

CC

GND

RAM ADDR.

REGISTER

B

REGISTER

ACC

TMP2

P0.0 - P0.7

PORT 0 DRIVERS

RAM

PORT 0

LATCH

TMP1

PORT 2 DRIVERS

PORT 2

LATCH

POINTER

P2.0 - P2.7

FLASH

STACK

PROGRAM

ADDRESS

REGISTER

BUFFER

PSEN

ALE/PROG

EA / V

RST

PC

ALU

INTERRUPT, SERIAL PORT,

AND TIMER BLOCKS

PSW

TIMING

AND

PP

CONTROL

OSC

INSTRUCTION

REGISTER

PORT 1

LATCH

PORT 1 DRIVERS

P1.0 - P1.7

PORT 3

LATCH

PORT 3 DRIVERS

P3.0 - P3.7

INCREMENTER

PROGRAM

COUNTER

DPTR

4-62

AT89C52

AT89C52

The AT89C52 provides th e foll owing stan dard features : 8K
bytes of Flash, 256 by tes o f RA M, 32 I/O l ines , th ree 1 6- bit
timer/counters, a six -vector two-lev el interru pt architectur e,
a full duplex serial port, on-chip oscillator , and clock c ir­cuitry. In addition, the AT89C52 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 interru pt system to continue fun ctioning.
The Power Down Mode saves the RA M contents but
freezes the oscillator , d is ablin g all other chip func tio ns un til
the next hardware reset.

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 high­impedance inputs.

Port 0 can also be configu red to be the multiplex ed low­order address/data bus during accesses to ex ternal pro­gram and data memory. In this mode, P0 has internal pul­lups.

Port 0 also rece ives th e code by tes dur ing Fla sh prog ram­ming and outputs the code bytes during program ver ifica­tion. External pu llups are requ ired during pr ogram v erific a­tion.

Port 1

Port 1 is an 8-bit bidire ction al I/O por t w ith inter nal pullu ps.
The Port 1 output buffers can sink/source four TTL inputs.
When 1s are written to Port 1 pins , they are p ulled hi gh 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

In addition, 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, as
shown in the following table.

Port 1 also receives the low-order address bytes during
Flash programming and verification.

Port Pin Alternate Functions

P1.0 T2 (external count input to Timer/Counter2),

P1.1 T2EX (Timer/Counter 2 capture/reload trigger

) because of the internal pullups.

IL

clock-out

and direction control)

Port 2

Port 2 is an 8-bit bidirectional I/O port with interna l pullups.
The Port 2 output buffers can sink/source four TTL inputs.
When 1s are writte n to Po rt 2 pi ns, they a re pul led 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

) because of the internal pullups.

IL

Port 2 emits the high-order address byte during fetches
from external program memory and during accesses to
external data memory th at u se 16 -b it a ddres s es ( MO VX @
DPTR). In this application, Port 2 uses strong internal pul­lups 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

Port 3 is an 8-bit bidirectional I/O port with interna l pullups.
The Port 3 output buffers can sink/source four TTL inputs.
When 1s are writte n to Po rt 3 pi ns, they a re pul led 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

) because of the pullups.

IL

Port 3 also serv es t he fun ctions of v arious spe cial f eatures
of the AT89C51, as shown in the following table.

Port 3 also receives some control signals for Flash pro­gramming and verification.

Port Pin Alternate Functions

P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR
P3.7 RD

(external interrupt 0)

(external data memory write strobe)

(external data memory read strobe)

RST

Reset input. A high on this pin for two machine cycles while
the oscillator is running resets the device.

ALE/PROG

Address Latch Enable is an output pulse for latching the
low byte of the address during accesses to external mem­ory. This pi n is al so t h e pr og ra m pu l se in p ut (PROG

) during

Flash programming.
In normal operation, ALE is emitted at a constant rate of 1/6

the oscillator frequency and may be used for external tim­ing or clocking purposes. Note, however, that one ALE

4-63

pulse is skipped durin g each access to extern al data me m­ory.

If desired, ALE operation can be disabled by setting bit 0 of
SFR location 8EH. With the bit set, ALE is active only dur­ing 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 pro­gram memory.

When the AT89C52 is executing code from external pro­gram memory, PSEN
cycle, except that two PSEN

is activated twice each machine

activations are skipped during

each access to external data memory.

/V

EA

PP

External Access Enable. EA must be strapped to GN D in
order to enable the device to fetch code from external pro­gram memory locations starting at 0000H up to FFFFH.
Note, however, that if lock bit 1 is programmed, EA

will be

internally latched on reset.

should be strapped to VCC for internal program execu-

EA
tions.

This pin also receives the 12-volt programming enable volt­age (V

) during Flash programming when 12-volt pro-

PP

gramming is selected.

XTAL1

Input to the inverting oscillator am plifier and input to the
internal clock operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

Table 1.

AT89C52 SFR Map and Reset Values

0F8H 0FFH

0F0H

0E8H 0EFH

0E0H

0D8H 0DFH

0D0H

0C8H

0C0H 0C7H

0B8H

0B0H

0A8H

0A0H

98H

90H

88H

80H

B

00000000

ACC

00000000

PSW

00000000

T2CON

00000000

IP

XX000000

P3

11111111

IE

0X000000

P2

11111111

SCON

00000000

P1

11111111

TCON

00000000

P0

11111111

T2MOD

XXXXXX00

SBUF

XXXXXXXX

TMOD

00000000

SP

00000111

RCAP2L

00000000

TL0

00000000

DPL

00000000

RCAP2H

00000000

TL1

00000000

DPH

00000000

TL2

00000000

TH0

00000000

TH2

00000000

TH1

00000000

PCON

0XXX0000

0F7H

0E7H

0D7H

0CFH

0BFH

0B7H

0AFH

0A7H

9FH

97H

8FH

87H

4-64

AT89C52

AT89C52

Special Function Registers

A map of the on-chip memory area called the Special Func­tion Register (SFR) space is shown in Table 1.

Note that not all of the addresses are occupied, and unoc­cupied addresses may not be implemented on the chip.
Read accesses to these addresses will in general return
random data, and write accesses will have an indetermi­nate effect.

User software should not write 1s to these unlisted loca­tions, since they may be used in future products to invoke

Table 2.

Symbol Function

TF2 Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set when either

EXF2 Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX and EXEN2 =

T2CON—Timer/Counter 2 Control Register

T2CON Address = 0C8H Reset Value = 0000 0000B
Bit Addressable
Bit TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2

76543210

RCLK = 1 or TCLK = 1.

1. When Timer 2 interrupt is enabled, EXF2 = 1 will cause the CPU to vector to the Timer 2 interrupt routine. EXF2
must be cleared by software. EXF2 does not cause an interrupt in up/down counter mode (DCEN = 1).

new features. In th at case, th e reset or inac tive valu es of
the new bits will always be 0.

Timer 2 Registers:

Control and status bits are contained
in registers T2CON (shown in Table 2) and T2MOD (shown
in Table 4) for Timer 2. The register pair (RCAP2H,
RCAP2L) are the Captu re/Reload re gisters for T imer 2 in
16-bit capture mode or 16-bit auto-reload mode.

Interrupt Registers:

The individual interrupt enable bits
are in the IE register. Two priorities can be set for each of
the six interrupt sources in the IP register.

CP/RL2

RCLK Receive clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock in serial

port Modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive clock.

TCLK Trans mit clock enable. When set, causes the serial port to use Timer 2 o v erf lo w puls es f o r its tr ansm it clock in serial

port Modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.

EXEN2 Timer 2 external enable. When set, allows a capture or reload to occur as a result of a negative transition on T2EX

if Timer 2 is not being used to clock the serial port. EXEN2 = 0 causes Timer 2 to ignore events at T2EX.
TR2 Start/Stop control for Timer 2. TR2 = 1 starts the timer.
C/T2

CP/RL2

Data Memory

The AT89C52 implements 256 bytes of on-chip RAM. The
upper 128 bytes oc cupy a parallel ad dress space to the
Special Function Register s. That means the u pper 128
bytes have the same addresses as the SFR space but are
physically separate from SFR space.

When an instruction accesses an internal location above
address 7FH, the address mode used in the instruction
specifies whether the CPU accesses the upper 128 bytes
of RAM or the SFR space. Instructions that use direct
addressing access SFR space.

Timer or counter select for Timer 2. C/T2 = 0 for timer function. C/T2 = 1 for external event counter (falling edge

triggered).

Capture/Reload select. CP/RL2 = 1 causes captures to occur on negativ e transit ions at T2EX if EXEN2 = 1. CP/RL2

= 0 causes automatic reloads to occur when Timer 2 overflows or negative transitions occur at T2EX when EXEN2

= 1. When either RCLK or TCLK = 1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow.

For example, the following direct addressing instruction
accesses the SFR at location 0A0H (which is P2).

MOV 0A0H, #data

Instructions that use indirect addressing access the upper
128 bytes of RAM. For example, the following indirect
addressing inst ructi on, where R0 contains 0A 0H, a cc es s es
the data byte at address 0A0H, rather than P2 (whose
address is 0A0H).

MOV @R0, #data

Note that stack operations are examples of indirect
addressing, so the upper 128 bytes of data RAM are avail ­able as stack space.

4-65

Timer 0 and 1

Timer 0 and Timer 1 in the AT89C52 operate the same way
as Timer 0 and Timer 1 i n the AT89C51.

Timer 2

Timer 2 is a 16-bit Timer/Counter that can operate as either
a timer or an event counter. The type of operation is
selected by bit C/T2
Timer 2 has three operating modes: capture, auto-reload
(up or down counting), and baud rate generator. The
modes are selected by bits in T2CON, as shown in Table 3.

Timer 2 consists of two 8- bi t regi st er s, TH2 and TL2. I n the
Timer function, the TL2 r egister is incremented ever y
machine cycle. Since a machine cycle consists of 12 oscil­lator periods, the count rate is 1/12 of the oscillator fre­quency.

Table 3.

RCLK +TCLK CP/RL2 TR2 MODE

Timer 2 Operating Modes

0 0 1 16-Bit Auto-Reload
0 1 1 16-Bit Capture
1 X 1 Baud Rate Generator

X X 0 (Off)

In the Counter function, the register is incremented in
response to a 1-to-0 transition at its corresponding external
input pin, T2. In thi s func tion, the extern al i nput is sa mpled
during S5P2 of every machin e cycle. When the samples

in the SFR T2 C ON (sh o w n i n Ta bl e 2).

show a high in one cycle and a low in the next cycle, the
count is incremented. The new count value appears in the
register during S3P1 of the cycle following the one in which
the transition was detected. Since two machine cycles (24
oscillator perio ds ) ar e re qui red to recognize a 1 -to -0 tr an si ­tion, the maximum count rate is 1/24 of the oscillator fre­quency. To ensure that a given level is sampled at least
once before it changes, the level should be held for at least
one full machine cycle.

Capture Mode

In the capture mode, two options are selected by bit
EXEN2 in T2CON. If EXEN2 = 0, Timer 2 is a 16-bit timer
or counter which upon overflow sets bit TF2 in T2CON.
This bit can then be used to generate an interrupt. If
EXEN2 = 1, Timer 2 p er forms t he sa me operation, but a 1 ­to-0 transition at external input T2EX also causes the cur­rent value in TH2 and TL2 to be captured into RCAP2H and
RCAP2L, resp ective ly. In addi tion, th e transit ion at T2E X
causes bit EXF2 in T2CON to be set. The EXF2 bit, like
TF2, can generate an interrupt. The capture mode is illus­trated in Figure 1.

Auto-Reload (Up or Down Counter)

Timer 2 can be programmed to count up or down when
configured in its 16-bit auto-reload mode. This feature is
invoked by the DCEN (Down Counter Enable) bit located in
the SFR T2MOD (see Table 4). Upon reset, the DCEN bit
is set to 0 so that ti mer 2 will defa ult to count u p. When
DCEN is set, Timer 2 c an coun t up o r dow n, depe nding on
the value of the T2EX pin.

Figure 1.

OSC

T2EX PIN

Timer in Capture Mode

÷12

T2 PIN

TRANSITION

DETECTOR

C/T2 = 0

C/T2 = 1

EXEN2

CONTROL

TR2

CAPTURE

CONTROL

TH2 TL2

RCAP2LRCAP2H

EXF2

TF2

OVERFLOW

TIMER 2

INTERRUPT

4-66

AT89C52

AT89C52

Figure 2 shows Timer 2 automaticall y counting up when
DCEN = 0. In this mode, two options are selected by bit
EXEN2 in T2CON. If EXEN2 = 0, Tim er 2 counts up to
0FFFFH and then sets the TF2 bit upon overflow. The over­flow also causes the tim er regi ste r s to be re loa ded with the
16-bit value in RCAP2H and RCAP2L. The valu es in Tim er
in Capture ModeRCAP 2H and RCAP2 L are pre set b y soft­ware. If EXEN2 = 1, a 16 -bit rel oad can be tr igger ed ei ther
by an overflow or by a 1-t o-0 transition at ex ternal input
T2EX. This transition also sets the EXF2 bit. Both the TF2
and EXF2 bits can generate an interrupt if enabled.

Setting the DCEN bit enabl es Time r 2 to coun t up o r d own ,
as shown in Figure 3. In this mode, the T2EX pin controls

Figure 2.

Timer 2 Auto Reload Mode (DCEN = 0)

OSC

T2 PIN

÷12

C/T2 = 0

C/T2 = 1

CONTROL

TR2

the direction of the count. A logic 1 at T2EX makes Timer 2
count up. The timer will overflow at 0FFFFH and set the
TF2 bit. This overfl ow also causes the 16-bit va lue in
RCAP2H and RCAP2L to be reloaded into the timer regis­ters, TH2 and TL2, respectively.

A logic 0 at T2EX makes Timer 2 count down. The timer
underflows when TH2 and TL2 equal the values stor ed in
RCAP2H and RCAP2L. The underflow sets the TF2 bit and
causes 0FFFFH to be reloaded into the timer registers.

The EXF2 bit toggles whenever Timer 2 overflows or
underflows and can be used as a 17th bit of resolution. In
this operating mode, EXF2 does not flag an interrupt.

TH2 TL2

OVERFLOW

RELOAD

TIMER 2

RCAP2LRCAP2H

INTERRUPT

TRANSITION

DETECTOR

T2EX PIN

CONTROL

EXEN2

Table 4.

Symbol Function

— Not implemented, reserved for future
T2OE Timer 2 Output Enable bit.
DCEN When set, this bit allows Timer 2 to be configured as an up/down counter.

T2MOD—Timer 2 Mode Control Register

T2MOD Address = 0C9H Reset Value = XXXX XX00B
Not Bit Addressable

——————T2OEDCEN

Bit76543210

TF2

EXF2

4-67