Rainbow Electronics AT89C55WD User Manual

Features

• Compatible with MCS

• 20K Bytes of Reprogrammable Flash Memory

• Endurance: 1000 Write/Erase Cycles

• 4V to 5.5V Operating Range

• FullyStaticOperation:0Hzto33MHz

• 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

• Interrupt Recovery from Power-down Mode

• Hardware Watchdog Timer

• Dual Data Pointer

• Power-off Flag

®

-51 Products

Description

8-bit
Microcontroller
with 20K Bytes
Flash

The AT89C55WD is a low-power, high-performance CMOS 8-bit microcontroller with
20K bytes of Flash programmable read only memory and 256 bytes of RAM. The
device is manufactured using Atmel’s high-density nonvolatile memory technology and
is compatible with the industry standard 80C51 and 80C52 instruction set and pinout.
The on-chip Flash allows the program memory to be user programmed by a conven­tional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash
on a monolithic chip, the Atmel AT89C55WD is a powerful microcomputer which pro­vides a highly flexible and cost effective solution to many embedded control
applications.

The AT89C55WD provides the following standard features: 20K bytes of Flash, 256
bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector, two-level interrupt
architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition,
the AT89C55WD 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 contents but freezes the
oscillator, disabling all other chip functions until the next external interrupt or hardware
reset.

AT89C55WD

Rev. 1921B–MICRO–09/02

1

Pin Configurations

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

TQFP

P1.4

P1.3

P1.2

P1.1 (T2 EX)

P1.0 (T2)NCVCC

P0.0 (AD0)

P0.1 (AD1)

P0.2 (AD2)

P0.3 (AD3)

4443424140393837363534

33

1
2
3
4
5
6

NC

7
8
9
10
11

1213141516171819202122

GND

GND

XTAL2

XTAL1

(A8) P2.0

(RD) P3.7

(WR) P3.6

(A9) P2.1

(A10) P2.2

32
31
30
29
28
27
26
25
24
23

(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

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
P1.3
P1.4
P1.5
P1.6
P1.7
RST

XTAL2
XTAL1

GND

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

(T2) P1.0

(T2EX) 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

PLCC

P1.4

P1.3

P1.2

P1.1 (T2 EX)

P1.0 (T2)NCVCC

65432

7
8
9
10
11
12
13
14
15
16
17

1819202122232425262728

1

40

VCC

39

P0.0 (AD0)

38

P0.1 (AD1)

37

P0.2 (AD2)

36

P0.3 (AD3)

35

P0.4 (AD4)

34

P0.5 (AD5)

33

P0.6 (AD6)

32

P0.7 (AD7)

31

EA/VPP

30

ALE/PROG

29

PSEN

28

P2.7 (A15)

27

P2.6 (A14)

26

P2.5 (A13)

25

P2.4 (A12)

24

P2.3 (A11)

23

P2.2 (A10)

22

P2.1 (A9)

21

P2.0 (A8)

P0.0 (AD0)

P0.1 (AD1)

P0.2 (AD2)

4443424140

P0.3 (AD3)

39

P0.4 (AD4)

38

P0.5 (AD5)

37

P0.6 (AD6)

36

P0.7 (AD7)

35

EA/VPP

34

NC

33

ALE/PROG

32

PSEN

31

P2.7 (A15)

30

P2.6 (A14)

29

P2.5 (A13)

NC

GND

XTAL2

XTAL1

(A8) P2.0

(RD) P3.7

(WR) P3.6

2

AT89C55WD

(A9) P2.1

(A10) P2.2

(A11) P2.3

(A12) P2.4

1921B–MICRO–09/0 2

Block Diagram

AT89C55WD

V

CC

GND

RAM ADDR.

REGISTER

B

REGISTER

ACC

TMP2

P0.0 - P0.7

PORT 0 DRIVERS

RAM

ALU

PORT 0

LATCH

TMP1

PORT 2 DRIVERS

PORT 2

LATCH

POINTER

P2.0 - P2.7

QUICK
FLASH

STACK

PROGRAM

ADDRESS

REGISTER

BUFFER

PC

INCREMENTER

PSEN

ALE/PROG

EA / V

RST

INTERRUPT, SERIAL PORT,

AND TIMER BLOCKS

PROGRAM

PSW

TIMING

AND

PP

CONTROL

OSC

INSTRUCTION

REGISTER

WATCH

DOG

PORT 1

LATCH

PORT 1 DRIVERS

P1.0 - P1.7

PORT 3

LATCH

PORT 3 DRIVERS

P3.0 - P3.7

COUNTER

DUAL
DPTR

1921B–MICRO–09/02

3

Pin Description

VCC Supply voltage.

GND Ground.

Port 0 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
during program verification. External pull-ups are required during program verification.

Port 1 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
internal pull-ups 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.

) because of the internal pull-ups.

IL

Port Pin Alternate Functions

P1.0 T2 (external count input to Timer/Counter 2), clock-out

P1.1 T2EX (Timer/Counter 2 capture/reload trigger and direction control)

Port 2 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 externally being
pulled low will source current (I

) because of the internal pull-ups.

IL

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 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 externally being
pulled low will source current (I

) because of the pull-ups.

IL

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

Port 3 also serves the functions of various special features of the AT89C55WD, as shown in
the following table.

4

AT89C55WD

1921B–MICRO–09/02

Port Pin Alternate Functions

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

AT89C55WD

P3.2 INT0

P3.3 INT1

P3.4 T0 (timer 0 external input)

P3.5 T1 (timer 1 external input)

P3.6 WR

P3.7 RD

(external interrupt 0)

(external interrupt 1)

(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. This pin drives High for 98 oscillator periods after the Watchdog times out. The DIS­RTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state
of bit DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address during
accesses to external memory. This pin is also the program pulse input (PROG

)duringFlash

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 pulse is
skipped during each access to external data memory.

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 AT89C55WD is executing code from external program memory, PSEN
twice each machine cycle, except that two PSEN

activations are skipped during each access

is activated

to external data memory.

EA

/VPP External Access Enable. EA must be strapped to GND 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

should be strapped to VCCfor internal program executions.

EA

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

will be internally latched on reset.

) during Flash programming.

PP

XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2 Output from the inverting oscillator amplifier.

1921B–MICRO–09/02

5

Table 1 . AT89C55WD 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

AUXR1

XXXXXXX0

TL0

00000000

DP0L

00000000

RCAP2H

00000000

TL1

00000000

DP0H

00000000

TL2

00000000

TH0

00000000

DP1L

00000000

TH2

00000000

TH1

00000000

DP1H

00000000

WDTRST

XXXXXXXX

AUX R

XXX00XX0

PCON

0XXX0000

0F7H

0E7H

0D7H

0CFH

0BFH

0B7H

0AFH

0A7H

9FH

97H

8FH

87H

Special Function Registers

6

AT89C55WD

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 new features. In that case, the reset or inactive values 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 2) for Timer 2. The register pair (RCAP2H, RCAP2L) are the
Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload mode.

1921B–MICRO–09/02

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.

Table 2 . T2CON—Timer/Counter 2 Control Register

T2CON Address = 0C8H Reset Value = 0000 0000B

Bit Addressable

AT89C55WD

Bit TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2

76543210

CP/RL2

Table 3 . AUXR: Auxiliary Register

AUXR Address = 8EH Reset Value = XXX00XX0B

Not Bit Addressable

–––WDIDLE DISRTO ––DISALE

Bit 7 6 5 4 3 2 1 0

– Reserved for future expansion

DISALE Disable/Enable ALE

DISALE Operating Mode

0 ALE is emitted at a constant rate of 1/6 the oscillator frequency

1 ALE is active only during a MOVX or MOVC instruction

DISRTO Disable/Enable Reset out

DISRTO Operating Mode

0 Reset pin is driven High after WDT times out

1 Reset pin is input only

WDIDLE Disable/Enable WDT in IDLE mode

WDIDLE Operating Mode

0 WDT continues to count in IDLE mode

1 WDT halts counting in IDLE mode

Dual Data Pointer Registers: To facilitate accessing both internal and external data memory,
two banks of 16-bit Data Pointer Registers are provided: DP0 at SFR address locations 82H­83H and DP1 at 84H-85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1.
The user should always initialize the DPS bit to the appropriate value before accessing the
respective Data Pointer Register.

Power Off Flag: The Power Off Flag (POF) is located at bit 4 (PCON.4) in the PCON SFR.
POF is set to “1” during power up. It can be set and rest under software control and is not
affected by reset.

1921B–MICRO–09/02

7

Table 4 . AUXR1: Auxiliary Register 1

AUXR1 Address = A2H Reset Value = XXXXXXX0B

Not Bit Addressable

––– – – – –DPS

Bit 7 6 5 4 3 2 1 0

– Reserved for future expansion

DPS Data Pointer Register Select

DPS

0 Selects DPTR Registers DP0L, DP0H

1 Selects DPTR Registers DP1L, DP1H

8

AT89C55WD

1921B–MICRO–09/02

AT89C55WD

Memory Organization

MCS-51 devices have a separate address space for Program and Data Memory. Up to
64 Kbytes each of external Program and Data Memory can be addressed.

Program Memory If the EA pin is connected to GND, all program fetches are directed to external memory.

On the AT89C55WD, if EA
4FFFH are directed to internal memory and fetches to addresses 5000H through FFFFH are
to external memory.

is connected to VCC, program fetches to addresses 0000H through

Data Memory The AT89C55WD implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a par-

allel address space to the Special Function Registers. That means the upper 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.

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 instruction, where R0 contains 0A0H, accesses 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 available as stack space.

1921B–MICRO–09/02

9

Hardware Watchdog Timer (One-time Enabled with Reset-out)

The WDT is intended as a recovery method in situations where the CPU may be subjected to
software upsets. The WDT consists of a 13-bit counter and the WatchDog Timer Reset
(WDTRST) SFR. The WDT is defaulted to disable from exiting reset. To enable the WDT, a
user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location 0A6H).
When the WDT is enabled, it will increment every machine cycle while the oscillator is running.
The WDT time-out period is dependent on the external clock frequency. There is no way to
disable the WDT except through reset (either hardware reset or WDT overflow reset). When
WDT overflows, it will drive an output RESET HIGH pulse at the RST pin.

Using the WDT To enable the WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register

(SFR location 0A6H). When the WDT is enabled, the user needs to service it by writing 01EH
and 0E1H to WDTRST to avoid a WDT overflow. The 13-bit counter overflows when it reaches
8191 (1FFFH), and this will reset the device. When the WDT is enabled, it will increment every
machine cycle while the oscillator is running. This means the user must reset the WDT at least
every 8191 machine cycles. To reset the WDT the user must write 01EH and 0E1H to
WDTRST. WDTRST is a write-only register. The WDT counter cannot be read or written.
When WDT overflows, it will generate an output RESET pulse at the RST pin. The RESET
pulse duration is 98xTOSC, where TOSC=1/FOSC. To make the best use of the WDT, it
should be serviced in those sections of code that will periodically be executed within the time
required to prevent a WDT reset.

WDT During Power-down and Idle

In Power-down mode the oscillator stops, which means the WDT also stops. While in Power­down mode, the user does not need to service the WDT. There are two methods of exiting
Power-down mode: by a hardware reset or via a level-activated external interrupt which is
enabled prior to entering Power-down mode. When Power-down is exited with hardware reset,
servicing the WDT should occur as it normally does whenever the AT89C55WD is reset. Exit­ing Power-down with an interrupt is significantly different. The interrupt is held low long
enough for the oscillator to stabilize. When the interrupt is brought high, the interrupt is ser­viced. To prevent the WDT from resetting the device while the interrupt pin is held low, the
WDT is not started until the interrupt is pulled high. It is suggested that the WDT be reset dur­ing the interrupt service for the interrupt used to exit Power-down.

To ensure that the WDT does not overflow within a few states of exiting Power-down, it is best
to reset the WDT just before entering Power-down.

Before going into the IDLE mode, the WDIDLE bit in SFR AUXR is used to determine whether
the WDT continues to count if enabled. The WDT keeps counting during IDLE (WDIDLE bit =

0) as the default state. To prevent the WDT from resetting the AT89C55WD while in IDLE
mode, the user should always set up a timer that will periodically exit IDLE, service the WDT,
and reenter IDLE mode.

With WDIDLE bit enabled, the WDT will stop to count in IDLE mode and resumes the count
upon exit from IDLE.

UART The UART in the AT89C55WD operates the same way as the UART in the AT89C51 and

AT89C52. For further information, see the December 1997 Microcontroller Data Book, page 2­48, section titled, “Serial Interface”.

10

AT89C55WD

1921B–MICRO–09/02

AT89C55WD

Timer 0 and 1 Timer 0 and Timer 1 in the AT89C55WD operate the same way as Timer 0 and Timer 1 in the

AT89C51 and AT89C52.

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
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 2.

Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2 register is
incremented every machine cycle. Since a machine cycle consists of 12 oscillator periods, the
count rate is 1/12 of the oscillator frequency.

Table 5 . Timer 2 Operating Modes

RCLK +TCLK CP/RL2 TR2 MODE

0 0 1 16-bit Auto-Reload

0 1 1 16-bit Capture

1 X 1 Baud Rate Generator

in the SFR T2CON (shown in Table 2). Timer 2 has

XX0(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 this function, the external input is sampled during S5P2 of
every machine cycle. When the samples 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 periods) are required to recognize a 1-to-0 transition, 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 performs the same operation, but a 1-to­0 transition at external input T2EX also causes the current value in TH2 and TL2 to be cap­tured into RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit
EXF2 in T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt. The capture
mode is illustrated in Figure 5.

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 6). Upon reset, the DCEN bit is set to 0 so that timer 2 will default to count
up. When DCEN is set, Timer 2 can count up or down, depending on the value of the T2EX
pin.

1921B–MICRO–09/02

11

Figure 5. Timer in Capture Mode

OSC

T2EX PIN

T2 PIN

÷12

TRANSITION

DETECTOR

C/T2 = 0

C/T2 = 1

EXEN2

CONTROL

TR2

CAPTURE

CONTROL

TH2 TL2

RCAP2LRCAP2H

EXF2

TF2

OVERFLOW

TIMER 2

INTERRUPT

Figure 6 shows Timer 2 automatically counting up when DCEN=0. In this mode, two options
are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 counts up to 0FFFFH and then
sets the TF2 bit upon overflow. The overflow also causes the timer registers to be reloaded
with the 16-bit value in RCAP2H and RCAP2L. The values in Timer in Capture ModeRCAP2H
and RCAP2L are preset by software. If EXEN2 = 1, a 16-bit reload can be triggered either by
an overflow or by a 1-to-0 transition at external 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 enables Timer 2 to count up or down, as shown in Figure 6. In this mode,
the T2EX pin controls 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 overflow also causes the 16-bit
value 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 stored 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.

12

AT89C55WD

1921B–MICRO–09/02

Figure 6. Timer 2 Auto Reload Mode (DCEN = 0)

AT89C55WD

OSC

T2 PIN

T2EX PIN

÷12

TRANSITION

DETECTOR

C/T2 = 0

C/T2 = 1

EXEN2

CONTR OL

TR2

RELOAD

CONTROL

TH2 TL2

RCAP2LRCAP2H

OVERFLOW

INTERRUPT

TF2

EXF2

Table 6 . T2MOD – Timer 2 Mode Control Register

T2MOD Address = 0C9H Reset Value = XXXX XX00B

Not Bit Addressable

––––––T2OE DCEN

Bit76543210

TIMER 2

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

1921B–MICRO–09/02

13

Figure 7. Timer 2 Auto Reload Mode (DCEN = 1)

(DOWN COUNTING RELOAD VALUE)

0FFH0FFH

TOGGLE

EXF2

OSC

12

÷

T2 PIN

C/T2 = 0

TR2

C/T2 = 1

Figure 8. Timer 2 in Baud Rate Generator Mode

NOTE: OSC. FREQ. IS DIVIDED BY 2, NOT 12

TH2 TL2

CONTROL

RCAP2LRCAP2H

(UP COUNTING RELOAD VALUE)

OVERFLOW

COUNT
DIRECTION
1=UP
0=DO

T2EX PIN

TIMER 1 OVERFLOW

2

÷

"0"

TF2

TIMER 2

INTERRUPT

"1"

SMOD1

14

OSC

T2 PIN

T2EX PIN

2

÷

TRANSITION

DETECTOR

AT89C55WD

C/T2 = 0

C/T2 = 1

TR2

EXEN2

CONTROL

CONTROL

TH2 TL2

RCAP2LRCAP2H

EXF2

"1"

"1"

TIMER 2

INTERRUPT

"0"

"0"

RCLK

16

÷

TCLK

÷

CLOCK

CLOCK

16

1921B–MICRO–09/02

Rx

Tx

AT89C55WD

Baud Rate Generator

Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON (Table

2). Note that the baud rates for transmit and receive can be different if Timer 2 is used for the
receiver or transmitter and Timer 1 is used for the other function. Setting RCLK and/or TCLK
puts Timer 2 into its baud rate generator mode, as shown in Figure 8.

The baud rate generator mode is similar to the auto-reload mode, in that a rollover in TH2
causes the Timer 2 registers to be reloaded with the 16-bit value in registers RCAP2H and
RCAP2L, which are preset by software.

The baud rates in Modes 1 and 3 are determined by Timer 2’s overflow rate according to the
following equation.

Modes 1 and 3 Baud Rates

The Timer can be configured for either timer or counter operation. In most applications, it is
configured for timer operation (CP/T2
is used as a baud rate generator. Normally, as a timer, it increments every machine cycle (at
1/12 the oscillator frequency). As a baud rate generator, however, it increments every state
time (at 1/2 the oscillator frequency). The baud rate formula is given below.

Modes 1 and 3

---------------------------------------

Baud Rate

= 0). The timer operation is different for Timer 2 when it

--------------------------------------------------------------------------------------=

32 x [65536-RCAP2H,RCAP2L)]

Timer 2 Overflow Rate

------------------------------------------------------------=

Oscillator Frequency

16

where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit
unsigned integer.

Timer 2 as a baud rate generator is shown in Figure 8. This figure is valid only if RCLK or
TCLK = 1 in T2CON. Note that a rollover in TH2 does not set TF2 and will not generate an
interrupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not
cause a reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus when Timer 2 is in use as a
baud rate generator, T2EX can be used as an extra external interrupt.

Note that when Timer 2 is running (TR2 = 1) as a timer in the baud rate generator mode, TH2
or TL2 should not be read from or written to. Under these conditions, the Timer is incremented
every state time, and the results of a read or write may not be accurate. The RCAP2 registers
may be read but should not be written to, because a write might overlap a reload and cause
write and/or reload errors. The timer should be turned off (clear TR2) before accessing the
Timer 2 or RCAP2 registers.

1921B–MICRO–09/02

15

Figure 9. Timer 2 in Clock-Out Mode

P1.0

(T2)

P1.1

(T2EX)

OSC

TRANSITION
DETECTOR

2

TR2

C/T2 BIT

EXF2

EXEN2

TL2

(8-BITS)

RCAP2L RCAP2H

2

TIMER 2
INTERRUPT

TH2

(8-BITS)

T2OE (T2MOD.1)

16

AT89C55WD

1921B–MICRO–09/02

AT89C55WD

Programmable Clock Out

A 50% duty cycle clock can be programmed to come out on P1.0, as shown in Figure 9. This
pin, besides being a regular I/O pin, has two alternate functions. It can be programmed to input
the external clock for Timer/Counter 2 or to output a 50% duty cycle clock ranging from 61 Hz
to 4 MHz for a 16 MHz operating frequency.

To configure the Timer/Counter 2 as a clock generator, bit C/T2
and bit T2OE (T2MOD.1) must be set. Bit TR2 (T2CON.2) starts and stops the timer.

The clock-out frequency depends on the oscillator frequency and the reload value of Timer 2
capture registers (RCAP2H, RCAP2L), as shown in the following equation.

Clock-Out Frequency

In the clock-out mode, Timer 2 roll-overs will not generate an interrupt. This behavior is similar
to when Timer 2 is used as a baud-rate generator. It is possible to use Timer 2 as a baud-rate
generator and a clock generator simultaneously. Note, however, that the baud-rate and clock­out frequencies cannot be determined independently from one another since they both use
RCAP2H and RCAP2L.

Oscillator Frequency

-------------------------------------------------------------------------------------=

4 x [65536-(RCAP2H,RCAP2L)]

(T2CON.1) must be cleared

Interrupts The AT89C55WD has a total of six interrupt vectors: two external interrupts (INT0 and INT1),

three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These interrupts are all
shown in Figure 10.

Each of these interrupt sources can be individually enabled or disabled by setting or clearing a
bit in Special Function Register IE. IE also contains a global disable bit, EA, which disables all
interrupts at once.

Note that Table 5 shows that bit position IE.6 is unimplemented. User software should not
write a ‘1’ to this bit position, since it may be used in future AT89 products.

Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register T2CON. Nei­ther of these flags is cleared by hardware when the service routine is vectored to. In fact, the
service routine may have to determine whether it was TF2 or EXF2 that generated the inter­rupt, and that bit will have to be cleared in software.

The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which the timers
overflow. The values are then polled by the circuitry in the next cycle. However, the Timer 2
flag, TF2, is set at S2P2 and is polled in the same cycle in which the timer overflows.

1921B–MICRO–09/02

17

Table 7 . Interrupt Enable (IE) Register

(MSB) (LSB)

EA

Enable Bit = 1 enables the interrupt.

Enable Bit = 0 disables the interrupt.

Symbol Position Function

EA IE.7 Disables all interrupts. If EA = 0, no interrupt is acknowledged. If EA

– IE.6 Reserved.

ET2 IE.5 Timer 2 interrupt enable bit.

ES IE.4 Serial Port interrupt enable bit.

ET1 IE.3 Timer 1 interrupt enable bit.

EX1 IE.2 External interrupt 1 enable bit.

ET0 IE.1 Timer 0 interrupt enable bit.

EX0 IE.0 External interrupt 0 enable bit.

– ET2 ES ET1 EX1 ET0 EX0

= 1, each interrupt source is individually enabled or disabled by
setting or clearing its enable bit.

User software should never write 1s to reserved bits, because they may be used in future AT89
products.

Figure 10. Interrupt Sources

0

INT0

TF0

INT1

TF1

1

0

1

TI

RI

IE0

IE1

18

TF2

EXF2

AT89C55WD

1921B–MICRO–09/02

AT89C55WD

Oscillator Characteristics

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be
configured for use as an on-chip oscillator, as shown in Figure 11. 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 12. 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 maximum voltage high
and low time specifications must be observed.

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 special functions
registers remain unchanged during this mode. The idle mode can be terminated by any
enabled interrupt or by a hardware reset.

Note that when idle mode is terminated by a hardware reset, the device normally resumes pro­gram execution 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 an unexpected write to a
port pin when idle mode is terminated by a reset, the instruction following the one that invokes
idle mode should not write to a port pin or to external memory.

Power-down Mode

In the Power-down mode, the oscillator is stopped, and the instruction that invokes Power­down is the last instruction executed. The on-chip RAM and Special Function Registers retain
their values until the Power-down mode is terminated. Exit from Power-down can be initiated
either by a hardware reset or by an enabled external interrupt. Reset redefines the SFRs but
does not change the on-chip RAM. The reset should not be activated before V
its normal operating level and must be held active long enough to allow the oscillator to restart
and stabilize.

is restored to

CC

Figure 11. Oscillator Connections

C2

C1

Note: C1, C2 = 30 pF ± 10 pF for Crystals

= 40 pF ± 10 pF for Ceramic Resonators

XTAL2

XTAL1

GND

1921B–MICRO–09/02

19

Figure 12. External Clock Drive Configuration

NC

EXTERNAL

OSCILLATOR

SIGNAL

XTAL2

XTAL1

GND

Table 8 . Status of External Pins During Idle and Power-down Modes

Mode Program Memory ALE PSEN PORT0 PORT1 PORT2 PORT3

Idle Internal 1 1 Data Data Data Data

Idle External 1 1 Float Data Address Data

Power-down Internal 0 0 Data Data Data Data

Power-down External 0 0 Float Data Data Data

20

AT89C55WD

1921B–MICRO–09/02

AT89C55WD

Program Memory Lock Bits

Programming the Flash

The AT89C55WD has three lock bits that can be left unprogrammed (U) or can be pro­grammed (P) to obtain the additional features listed in the following table.

Table 9 . Lock Bit Protection Modes

Program Lock Bits

Protection TypeLB1 LB2 LB3

1 U U U No program lock features.

MOVC instructions executed from external program memory are

2PUU

3 P P U Same as mode 2, but verify is also disabled.

4 P P P Same as mode 3, but external execution is also disabled.

When lock bit 1 is programmed, the logic level at the EA
reset. If the device is powered up without a reset, the latch initializes to a random value and
holds that value until reset is activated. The latched value of EA
logic level at that pin in order for the device to function properly.

The AT89C55WD is shipped with the on-chip Flash memory array ready to be programmed.
The programming interface needs a high-voltage (12-volt) program enable signal and is com­patible with conventional third-party Flash or EPROM programmers.

disabled from fetching code bytes from internal memory, EA
sampled and latched on reset, and further programming of the Flash
memory is disabled.

pin is sampled and latched during

must agree with the current

is

The AT89C55WD code memory array is programmed byte-by-byte.

Programming Algorithm: Before programming the AT89C55WD, the address, data, and
control signals should be set up according to the Flash programming mode table and Figures
13 and 14. To program the AT89C55WD, take the following steps:

1. Input the desired memory location on the address lines.

2. Input the appropriate data byte on the data lines.

3. Activate the correct combination of control signals.

4. Raise EA

5. Pulse ALE/PROG
write cycle is self-timed and typically takes no more than 50 µs. Repeat steps 1
through 5, changing the address and data for the entire array or until the end of the
object file is reached.

Chip Erase Sequence: Before the AT89C55WD can be reprogrammed, a Chip Erase opera­tion needs to be performed. To erase the contents of the AT89C55WD, follow this sequence:

1. Raise V

2. Pulse ALE/PROG

3. Wait for 150 ms.

4. Power V

5. Pulse ALE/PROG

6. Wait for 150 ms.

7. Power V

Polling: The AT89C55WD features Data Polling to indicate the end of a write cycle. Dur-

Data

ing a write cycle, an attempted read of the last byte written will result in the complement of the
written data on P0.7. Once the write cycle has been completed, true data is valid on all out-

/VPPto 12V.

oncetoprogramabyteintheFlasharrayorthelockbits.Thebyte-

to 6.5V.

CC

once (duration of 200 - 500 ns).

down and up to 6.5V.

CC

once (duration of 200 - 500 ns).

down and up to 6.5V.

CC

1921B–MICRO–09/02

21

puts,andthenextcyclemaybegin.DataPolling may begin any time after a write cycle has
been initiated.

Ready/Busy

put signal. P3.0 is pulled low after ALE goes high during programming to indicate BUSY
is pulled high again when programming is done to indicate READY.

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 status of the individ­ual lock bits can be directly verified by reading them back.

Reading the Signature Bytes: The signature bytes are read by the same procedure as a nor­mal verification of locations 000H, 100H, and 200H, except that P3.6 and P3.7 must be pulled
to a logic low. The values returned are as follows:

: The progress of byte programming can also be monitored by the RDY/BSY out-

.P3.0

(000H) = 1EH indicates manufactured by Atmel
(100H) = 55H
(200H) = 06H indicates 89C55WD

22

AT89C55WD

1921B–MICRO–09/02

AT89C55WD

Programming Interface

Every code byte in the Flash array can be programmed by using the appropriate combination
of control signals. The write operation cycle is self-timed and once initiated, will automatically
time itself to completion.

Most worldwide major programming vendors offer support for the Atmel microcontroller series.
Please contact your local programming vendor for the appropriate software revision.

Table 1 0. Flash Programming Modes

ALE/

Mode V

WriteCodeData 5V H L

Read Code Data 5V H L H H/12V L L L H H D

Write Lock Bit 1 6.5V H L

Write Lock Bit 2 6.5V H L

Write Lock Bit 3 6.5V H L

Read Lock Bits
1, 2, 3

Chip Erase 6.5V H L

RST PSEN

CC

5V H L H H H H L H L

PROG

EA/
V

(1)

12V L H H H H D

(2)

12V H H H H H X X X X

(2)

12V H H H L L X X X X

(2)

12V H L H H L X X X X

(3)

12V H L H L L X X X X

P2.6 P2.7 P3.3 P3.6 P3.7

PP

P0.7-0

Data

IN

OUT

P0.2,
P0.3,

P0.4

P3.4 P2.5-0 P1.7-0

Address

A14 A13 -8 A7-0

A14 A13 -8 A7-0

XX X

Read Atmel ID 5V H L H H L L L L L 1EH X XX 0000 00H

Read Device ID 5V H L H H L L L L L 55H X XX 0001 00H

Read Device ID 5V H L H H L L L L L 06H X XX 0010 00H

Notes: 1. Write Code Data requires a 200 ns PROG pulse.

2. Write Lock Bits requires a 100 µs PROG

3. Chip Erase requires a 200 ns - 500 ns PROG

4. RDY/BSY

signal is output on P3.0 during programming.

pulse.

pulse.

1921B–MICRO–09/02

23

Figure 13. Programming the Flash Memory

ADDR.

0000H/4FFFH

SEE FLASH

PROGRAMMING

MODES TABLE

A0 - A7

A8 - A13

A14*

AT89C55WD

P1.0 - P1.7

P2.0 - P2.5
P3.4
P2.6

P2.7
P3.3
P3.6

P3.7

XTAL2 EA

V

P0

ALE

4.5V to 5.5V

CC

PGM
DATA

PROG

V/V

IH PP

3 - 33 MHz

Figure 14. Verifying the Flash Memory

ADDR.

0000H/4FFFH

SEE FLASH

PROGRAMMING

MODES TABLE

3 - 33 MHz

A0 - A7

A8 - A13

A14*

P3.0

1

XTAL

GND

RST

PSEN

AT89C55WD

P1.0 - P1.7

P2.0 - P2.5
P3.4

P2.6
P2.7

P3.3
P3.6
P3.7

XTAL 2 EA

V

P0

ALE

4.5V to 5.5V

CC

RDY/
BSY

V

IH

PGM DATA
(USE 10K
PULL-UPS)

V

IH

24

Note: *Programming address line A14 (P3.4) is not the same as the external memory address line

AT89C55WD

A14 (P2.6).

XTAL1

GND

RST

PSEN

V

IH

1921B–MICRO–09/02

AT89C55WD

Flash Programming and Verification Characteristics

TA=20°Cto30°C, VCC=4.5Vto5.5V

Symbol Parameter Min Max Units

V

PP

I

PP

I

CC

1/t

t

AVGL

t

GHAX

t

DVG L

t

GHDX

t

EHSH

t

SHGL

t

GHSL

t

GLGH

t

AVQ V

t

ELQV

t

EHQZ

t

GHBL

t

WC

CLCL

Programming Supply Voltage 11.5 12.5 V

Programming Supply Current 10 mA

VCCSupply Current 30 mA

Oscillator Frequency 3 33 MHz

Address Setup to PROG Low 48t

Address Hold After PROG 48t

Data Setup to PROG Low 48t

Data Hold After PROG 48t

P2.7 (ENABLE)HightoV

PP

48t

CLCL

CLCL

CLCL

CLCL

CLCL

VPPSetup to PROG Low 10 µs

VPPHold After PROG 10 µs

PROG Width 0.2 1 µs

Address to Data Valid 48t

ENABLE Low to Data Valid 48t

Data Float After ENABLE 048t

CLCL

CLCL

CLCL

PROG High to BUSY Low 1.0 µs

Byte Write Cycle Time 80 µs

1921B–MICRO–09/02

25

Flash Programming and Verification Waveforms

P1.0 - P1.7
P2.0 - P2.5

P3.4

PORT 0

ALE/PROG

EA/V

PP

P2.7

(ENABLE)

P3.0

(RDY/BSY)

Lock Bit Programming

Test Conditions

Setup

t

AVGL

t

SHGL

PROGRAMMING

ADDRESS

DATA I N

V

t

EHSH

t

PP

DVG L

t

GLGH

t

GHBL

t

GHDX

t

t

ELQV

GHAX

t

GHSL

LOGIC 1
LOGIC 0

BUSY

t

WC

VERIFICATION

ADDRESS

t

AVQV

DATA O U T

READY

t

EHQZ

Lockbit_1, 2 or 3

Data Setup

ALE/PROG

V

= 6.5V

CC

100 µs

V

= 4.5V to 5.5V

CC

Wait 10 ms to reload
new lock bit status

26

AT89C55WD

1921B–MICRO–09/02

Parallel Chip Erase Mode

AT89C55WD

Test Conditions

Setup

ALE/PROG

P3<0>

= 6.5V

V

CC

200 ns

Erase

DC

Erase

10 ms

Test Conditions Setup

200 ns

Erase

DC

Erase

V

= 4.5V to 5.5V

CC

Wait 10 ms before

reprogramming

1921B–MICRO–09/02

27

Absolute Maximum Ratings*

Operating Temperature .................................. -55°Cto+125°C

Storage Temperature ..................................... -65°Cto+150°C

Voltage on Any Pin

with Respect to Ground ..................................... -1.0V to +7.0V

Maximum Operating Voltage ............................................ 6.6V

DC Output Current ...................................................... 15.0 mA

*NOTICE: Stresses beyond those listed under “Absolute

Maximum Ratings” may cause permanent dam­age to the device. This is a stress rating only and
functional operation of the device at these or any
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect
device reliability.

DC Characteristics

The values shown in this table are valid for TA=-40°Cto85°C and VCC= 4.0V to 5.5V, unless otherwise noted.

Symbol Parameter Condition Min Max Units

V

IL

V

IL1

V

IH

V

IH1

V

OL

V

OL1

V

OH

V

OH1

I

IL

I

TL

I

LI

Input Low Voltage (Except EA)-0.50.2V

Input Low Voltage (EA)-0.50.2V

-0.1 V

CC

-0.3 V

CC

Input High Voltage (Except XTAL1, RST) 0.2 VCC+0.9 VCC+0.5 V

Input High Voltage (XTAL1, RST) 0.7 V

Output Low Voltage

Output Low Voltage

Output High Voltage
(Ports 1,2,3, ALE, PSEN

Output High Voltage
(Port 0 in External Bus Mode)

(1)

(Ports 1,2,3) IOL=1.6mA 0.45 V

(1)

(Port 0, ALE, PSEN)IOL=3.2mA 0.45 V

= -60 µA, VCC=5V± 10% 2.4 V

I

OH

= -25 µA 0.75 V

I

)

OH

I

= -10 µA 0.9 V

OH

I

=-800µA,VCC=5V± 10% 2.4 V

OH

I

=-300µA 0.75V

OH

I

= -80 µA 0.9 V

OH

CC

CC

CC

CC

CC

VCC+0.5 V

V

V

V

V

Logical 0 Input Current (Ports 1,2,3) VIN= 0.45V -50 µA

Logical 1 to 0 Transition Current (Ports 1,2,3) VIN=2V,VCC=5V± 10% -650 µA

Input Leakage Current (Port 0, EA)0.45<V

IN<VCC

±10 µA

RRST Reset Pulldown Resistor 10 30 kΩ

C

IO

Pin Capacitance Test Freq. = 1 MHz, TA=25°C10pF

Active Mode, 12 MHz 25 mA

Power Supply Current

I

CC

Power-down Mode

(1)

Idle Mode, 12 MHz 6.5 mA

VCC= 5.5V 100 µA

Notes: 1. Under steady state (non-transient) conditions, IOLmust be externally limited as follows:

Maximum I
Maximum I

perportpin:10mA

OL

per 8-bit port:

OL

Port0:26mA Ports1,2,3:15mA
Maximum total I
If I

exceeds the test condition, VOLmay exceed the related specification. Pins are not guaranteed to sink current greater

OL

for all output pins: 71 mA

OL

than the listed test conditions.

28

2. Minimum V

AT89C55WD

for Power-down is 2V.

CC

1921B–MICRO–09/02

AT89C55WD

AC Characteristics

Under operating conditions, load capacitance for Port 0, ALE/PROG, and PSEN =100pF;
load capacitance for all other outputs = 80 pF.

External Program and Data Memory Characteristics

12 MHz Oscillator Variable Oscillator

Symbol Parameter

1/t

t

LHLL

t

AVLL

t

LLAX

t

LLIV

t

LLPL

t

PLPH

t

PLIV

t

PXIX

t

PXIZ

t

PXAV

t

AVI V

t

PLAZ

t

RLRH

t

WLWH

t

RLDV

t

RHDX

t

RHDZ

t

LLDV

t

AVDV

t

LLWL

t

AVWL

t

QVWX

t

QVWH

t

WHQX

t

RLAZ

t

WHLH

CLCL

Oscillator Frequency 0 33 MHz

ALE Pulse Width 127 2t

Address Valid to ALE Low 43 t

Address Hold After ALE Low 48 t

ALE Low to Valid Instruction In 233 4t

ALE Low to PSEN Low 43 t

PSEN Pulse Width 205 3t

PSEN Low to Valid Instruction In 145 3t

Input Instruction Hold After PSEN 00ns

Input Instruction Float After PSEN 59 t

PSEN to Address Valid 75 t

Address to Valid Instruction In 312 5t

PSEN Low to Address Float 10 10 ns

RD Pulse Width 400 6t

WR Pulse Width 400 6t

RD Low to Valid Data In 252 5t

Data Hold After RD 00ns

Data Float After RD 97 2t

ALE Low to Valid Data In 517 8t

Address to Valid Data In 585 9t

ALE Low to RD or WR Low 200 300 3t

Address to RD or WR Low 203 4t

Data Valid to WR Transition 23 t

Data Valid to WR High 433 7t

Data Hold After WR 33 t

RD Low to Address Float 0 0 ns

RD or WR High to ALE High 43 123 t

-40 ns

CLCL

-25 ns

CLCL

-25 ns

CLCL

-65 ns

CLCL

-25 ns

CLCL

-45 ns

CLCL

-60 ns

CLCL

-25 ns

CLCL

-8 ns

CLCL

-80 ns

CLCL

-100 ns

CLCL

-100 ns

CLCL

-90 ns

CLCL

-28 ns

CLCL

-150 ns

CLCL

-165 ns

CLCL

-50 3t

CLCL

-75 ns

CLCL

-30 ns

CLCL

-130 ns

CLCL

-25 ns

CLCL

-25 t

CLCL

+50 ns

CLCL

+25 ns

CLCL

UnitsMin Max Min Max

1921B–MICRO–09/02

29

External Program Memory Read Cycle

t

LHLL

ALE

t

AVLL

t

LLPL

PSEN

t

LLAX

PORT 0

A0 - A7 A0 - A7

t

AVIV

PORT 2

External Data Memory Read Cycle

t

LHLL

ALE

t

PLAZ

A8 - A15

t

LLIV

t

PLIV

t

PXIZ

t

PXIX

INSTR IN

t

PLPH

t

PXAV

t

WHLH

A8 - A15

PSEN

RD

PORT 0

PORT 2

t

LLDV

t

LLWL

t

LLAX

t

AVLL

A0 - A7 FROM RI OR DPL

t

AVWL

P2.0 - P2.7 OR A8 - A15 FROM DPH

t

AVDV

t

RLAZ

t

RLRH

t

RLDV

DATA IN INSTR IN

t

RHDZ

t

RHDX

A0 - A7 FROM PCL

A8 - A15 FROM PCH

30

AT89C55WD

1921B–MICRO–09/02

External Data Memory Write Cycle

t

LHLL

ALE

PSEN

t

LLWL

t

WLWH

t

WHLH

AT89C55WD

WR

t

AVLL

PORT 0

PORT 2

A0 - A7 FROM RI OR DPL

t

AVWL

P2.0 - P2.7 OR A8 - A15 FROM DPH

External Clock Drive Waveforms

t

0.7 V

CC

CHCX

CC

0.45V

V - 0.5V

CC

0.2 V - 0.1V

t

LLAX

t

QVWX

t

t

QVWH

DATA OUT INSTR IN

t

CLCH

t

CLCX

WHQX

A0 - A7 FROM PCL

A8 - A15 FROM PCH

t

CHCX

t

CLCL

t

CHCL

External Clock Drive

Symbol Parameter Min Max Units

1/t

CLCL

t

CLCL

t

CHCX

t

CLCX

t

CLCH

t

CHCL

1921B–MICRO–09/02

Oscillator Frequency 0 33 MHz

Clock Period 30 ns

High Time 12 ns

Low Time 12 ns

Rise Time 5 ns

Fall Time 5 ns

31

Serial Port Timing: Shift Register Mode Test Conditions

The values in this table are valid for VCC= 4.0V to 5.5V and Load Capacitance = 80 pF.

12 MHz Osc Variable Oscillator

Symbol Parameter

t

XLXL

t

QVXH

t

XHQX

t

XHDX

t

XHDV

Serial Port Clock Cycle Time 1.0 12t

Output Data Setup to Clock Rising Edge 700 10t

Output Data Hold After Clock Rising Edge 50 2t

Input Data Hold After Clock Rising Edge 0 0 ns

Clock Rising Edge to Input Data Valid 700 10t

Shift Register Mode Timing Waveforms

INSTRUCTION

ALE

CLOCK

WRITE TO SBUF

OUTPUT DATA

CLEAR RI

INPUT DATA

0

t

QVXH

1

t

XHDV

0

2

t

XLXL

t

XHQX

1

VALID VALIDVALID VALIDVALID VALIDVALID VALID

3

2

t

XHDX

UnitsMin Max Min Max

CLCL

-133 ns

CLCL

-80 ns

CLCL

-133 ns

CLCL

4

3

5

4

6

5

7

8

6

µs

7

SET TI

SET RI

AC Testing Input/Output Waveforms

V - 0.5V

CC

0.45V

(1)

0.2 V + 0.9V

TEST POINTS

0.2 V - 0.1V

CC

CC

Note: 1. AC Inputs during testing are driven at VCC- 0.5V for a logic 1 and 0.45V for a logic 0. Timing measurements are made at V

min. for a logic 1 and VILmax. for a logic 0.

Float Waveforms

(1)

V

LOAD

V

V

LOAD

LOAD

+ 0.1V

- 0.1V

Timing Reference

Points

- 0.1V

V

OL

+ 0.1V

V

OL

Note: 1. For timing purposes, a port pin is no longer floating when a 100 mV change from load voltage occurs. A port pin begins to

float when a 100 mV change from the loaded V

OH/VOL

level occurs.

IH

32

AT89C55WD

1921B–MICRO–09/02

Ordering Information

Speed

(MHz)

24 4.0V to 5.5V AT89C55WD-24AC

33 4.5V to 5.5V AT89C55WD-33AC

Power

Supply Ordering Code Package Operation Range

AT89C55WD-24JC
AT89C55WD-24PC

AT89C55WD-24AI

AT89C55WD-24JI
AT89C55WD-24PI

AT89C55WD-33JC

AT89C55WD-33PC

44A
44J
40P6

44A

44J
40P6

44A
44J

40P6

AT89C55WD

Commercial

(0°Cto70°C)

Industrial

(-40°Cto85°C)

Commercial

(0°Cto70°C)

Package Type

44A 44-lead, Thin Plastic Gull Wing Quad Flatpack (TQFP)

44J 44-lead, Plastic J-leaded Chip Carrier (PLCC)

40P6 40-pin, 0.600" Wide, Plastic Dual Inline Package (PDIP)

1921B–MICRO–09/02

33

Package Information

44A – TQFP

PIN 1

B

PIN 1 IDENTIFIER

e

E1 E

D1

D

C

0˚~7˚

A1

L

Notes: 1. This package conforms to JEDEC reference MS-026, Variation ACB.

2. Dimensions D1 and E1 do not include mold protrusion. Allowable
protrusion is 0.25 mm per side. Dimensions D1 and E1 are maximum
plastic body size dimensions including mold mismatch.

3. Lead coplanarity is 0.10 mm maximum.

A2 A

SYMBOL

COMMON DIMENSIONS

(Unit of Measure = mm)

MIN

A – – 1.20

A1 0.05 – 0.15

A2 0.95 1.00 1.05

D 11.75 12.00 12.25

D1 9.90 10.00 10.10 Note 2

E 11.75 12.00 12.25

E1 9.90 10.00 10.10 Note 2

B 0.30 – 0.45

C 0.09 – 0.20

L 0.45 – 0.75

e 0.80 TYP

NOM

MAX

NOTE

34

2325 Orchard Parkway

R

San Jose, CA 95131

AT89C55WD

TITLE

44A, 44-lead, 10 x 10 mm Body Size, 1.0 mm Body Thickness,

0.8 mm Lead Pitch, Thin Profile Plastic Quad Flat Package (TQFP)

10/5/2001

DRAWING NO.

44A

1921B–MICRO–09/02

REV.

B

44J–PLCC

AT89C55WD

1.14(0.045) X 45˚

B

e

0.51(0.020)MAX

45˚ MAX (3X)

Notes: 1. This package conforms to JEDEC reference MS-018, Variation AC.

2. Dimensions D1 and E1 do not include mold protrusion.

Allowable protrusion is .010"(0.254 mm) per side. Dimension D1
and E1 include mold mismatch and are measured at the extreme
material condition at the upper or lower parting line.

3. Lead coplanarity is 0.004" (0.102 mm) maximum.

PIN NO. 1

IDENTIFIER

D1

D

1.14(0.045) X 45˚

E1 E

0.318(0.0125)

0.191(0.0075)

NOM

D2/E2

MAX

B1

A2

A1

A

COMMON DIMENSIONS

(Unit of Measure = mm)

SYMBOL

A 4.191 – 4.572

A1 2.286 – 3.048

A2 0.508 ––

D 17.399 – 17.653

D1 16.510 – 16.662 Note 2

E 17.399 – 17.653

E1 16.510 – 16.662 Note 2

D2/E2 14.986 – 16.002

B 0.660 – 0.813

B1 0.330 – 0.533

e 1.270 TYP

MIN

NOTE

2325 Orchard Parkway

R

San Jose, CA 95131

1921B–MICRO–09/02

TITLE

44J, 44-lead, Plastic J-leaded Chip Carrier (PLCC)

DRAWING NO.

44J

10/04/01

REV.

B

35

40P6 – PDIP

PIN

1

E1

A1

B

REF

E

B1

C

L

SEATING PLANE

A

D

e

0º ~ 15º

eB

Notes: 1. This package conforms to JEDEC reference MS-011, Variation AC.

2. Dimensions D and E1 do not include mold Flash or Protrusion.
Mold Flash or Protrusion shall not exceed 0.25 mm (0.010").

TITLE

2325 Orchard Parkway

R

San Jose, CA 95131

40P6, 40-lead (0.600"/15.24 mm Wide) Plastic Dual
Inline Package (PDIP)

COMMON DIMENSIONS

(Unit of Measure = mm)

SYMBOL

A ––4.826

A1 0.381 ––

D 52.070 – 52.578 Note 2

E 15.240 – 15.875

E1 13.462 – 13.970 Note 2

B 0.356 – 0.559

B1 1.041 – 1.651

L 3.048 – 3.556

C 0.203 – 0.381

eB 15.494 – 17.526

e 2.540 TYP

MIN

NOM

MAX

DRAWING NO.

40P6

NOTE

09/28/01

REV.

B

36

AT89C55WD

1921B–MICRO–09/02

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© Atmel Corporation 2002.

Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company’s standard warranty
whichisdetailedinAtmel’s Terms and Conditions located on the Company’s web site. The Company assumes no responsibility for any errors
which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and does
not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are granted
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ATM EL®is a registered trademark of Atmel.

®

MCS

-51 is a registered trademark of Intel Corporation.

Other terms and product names may be the trademarks of others.

Printed on recycled paper.

1921B–MICRO–09/02 xM