80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Product data
Supersedes data of 1999 Oct 27
IC28 Data Handbook
2002 Jan 15
Page 2
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
DESCRIPTION
The 89C51/89C52/89C54/89C58 contain a non-volatile FLASH
program memory that is parallel programmable. For devices that are
serial programmable (In-System Programmable (ISP) and
In-Application Programmable (IAP) with a boot loader), see the
89C51Rx2 or 89C66x datasheets.
All three families are Single-Chip 8-bit Microcontrollers
manufactured in advanced CMOS process and are derivatives of
the 80C51 microcontroller family. All the devices have the same
instruction set as the 80C51.
89C51/89C52/89C54/89C58
ISP/IAP devices
(see separate data sheets)
MTP = Multi-Time Programming (via parallel programmer)
ISP = In-System Programming (via serial interface)
IAP = In-Application Programming
Please note that the FLASH programming algorithm for these parts has been modified. Please see the Device Comparison table for details.
DEVICE COMPARISON TABLE
ItemOld devicesNew devicesReason for change
Type descriptionP89C5xUBxx / P89C5xUFxxP89C5xBxLetter U dropped for shorter type
Programming algorithmWhen using parallel programmer,
Quad Flat Package typePQFP package (P89C5xUxBB)PQFP package replaced by
Package identifiersPLCC = AA
Flash memory program and
erase cycles
Power consumptionActive mode: I
be sure to select P89C5xUxxx
devices
PQFP = BB
PDIP = PN
100 program and erase cycles10,000 program and erase
=
(0.9 FREQ. + 20)mA
Idle mode: I
(0.37 FREQ. + 1.0)mA
CC(MAX)
CC(MAX)
=
When using a parallel programmer, be sure to select P89C5xBx
devices (no more letter U). IF
DEVICES ARE NOT YET SELECTABLE, ASK YOUR VENDOR FOR A SOFTWARE UPDATE.
LQFP package (P89C5xBBD).
SEE NEW DIMENSIONS AT
THE END OF THIS DATA
SHEET.
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
PIN DESCRIPTIONS
PIN NUMBER
MNEMONICDIPLCCQFPTYPE NAME AND FUNCTION
V
SS
V
CC
P0.0–0.739–32 43–36 37–30I/OPort 0: Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that have 1s written to
P1.0–P1.71–82–940–44,
P2.0–P2.721–28 24–31 18–25I/OPort 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2 pins that have 1s
P3.0–P3.710–1711,
RST9104IReset: A high on this pin for two machine cycles while the oscillator is running, resets the
ALE303327OAddress Latch Enable: Output pulse for latching the low byte of the address during an
PSEN293226OProgram Store Enable: The read strobe to external program memory. When executing
EA/V
PP
XTAL1192115ICrystal 1: Input to the inverting oscillator amplifier and input to the internal clock
XTAL2182014OCrystal 2: Output from the inverting oscillator amplifier.
NOTE: To avoid “latch-up” effect at power-on, the voltage on any pin (other than VPP) at any time must not be higher than VCC + 0.5 V or
V
– 0.5 V , respectively.
SS
202216IGround: 0 V reference.
404438IPower Supply: This is the power supply voltage for normal, idle, and power-down operation.
them float and can be used as high-impedance inputs. Port 0 is also the multiplexed
low-order address and data bus during accesses to external program and data memory. In
this application, it uses strong internal pull-ups when emitting 1s.
1–3
1240I/OT2 (P1.0): T imer/Counter2 external count input/clockout (see Programmable Clock-Out).
2341IT2EX (P1.1): Timer/Counter2 reload/capture/direction control.
13–195,7–13
10115IRxD (P3.0): Serial input port
11137OTxD (P3.1): Serial output port
12148IINT0 (P3.2): External interrupt
13159IINT1 (P3.3): External interrupt
141610IT0 (P3.4): Timer 0 external input
151711IT1 (P3.5): Timer 1 external input
161812OWR (P3.6): External data memory write strobe
171913ORD (P3.7): External data memory read strobe
313529IExternal Access Enable/Programming Supply Voltage: EA must be externally held low
I/OPort 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. Port 1 pins that have 1s
written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs,
port 1 pins that are externally pulled low will source current because of the internal pull-ups.
(See DC Electrical Characteristics: I
written to them 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 because of the internal
pull-ups. (See DC Electrical Characteristics: I
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
pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses
(MOV @Ri), port 2 emits the contents of the P2 special function register.
I/OPort 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s
written to them 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 because of the pull-ups.
(See DC Electrical Characteristics: I
89C51/89C52/89C54/89C58, as listed below:
device. An internal diffused resistor to V
capacitor to V
access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6 the
oscillator frequency , and can be used for external timing or clocking. Note that one ALE
pulse is skipped during each access to external data memory. ALE can be disabled by
setting SFR auxiliary.0. With this bit set, ALE will be active only during a MOVX instruction.
code from the external program memory, PSEN
except that two PSEN
is not activated during fetches from internal program memory.
PSEN
to enable the device to fetch code from external program memory locations 0000H to the
maximum internal memory boundary. If EA
program memory unless the program counter contains an address greater than 0FFFH for
4 k devices, 1FFFH for 8 k devices, 3FFFH for 16 k devices, and 7FFFH for 32 k devices.
The value on the EA
have no effect. This pin also receives the 5V/12V (±10%) programming supply voltage (V
during FLASH programming.
generator circuits.
.
CC
activations are skipped during each access to external data memory.
pin is latched when RST is released and any subsequent changes
89C51/89C52/89C54/89C58
). Alternate function for Port 1:
IL
). Port 2 emits the high-order address byte
IL
). Port 3 also serves the special features of the
IL
permits a power-on reset using only an external
SS
is activated twice each machine cycle,
is held high, the device executes from internal
PP
)
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Table 1. 89C51/89C52/89C54/89C58 Special Function Registers
TH0Timer High 08CH00H
TH1Timer High 18DH00H
TH2#Timer High 2CDH00H
TL0Timer Low 08AH00H
TL1Timer Low 18BH00H
TL2#Timer Low 2CCH00H
TMODTimer Mode89HGATEC/TM1M0GATEC/TM1M000H
* SFRs are bit addressable.
# SFRs are modified from or added to the 80C51 SFRs.
– Reserved bits.
1. Reset value depends on reset source.
2. Bit will not be affected by reset.
SM0/FE
8F8E8D8C8B8A8988
CFCECDCCCBCAC9C8
SM1SM2RENTB8RB8TIRI00H
2
GF1GF0PDIDL00xxx000B
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
FLASH EPROM MEMORY
General Description
The 89C51/89C52/89C54/89C58 FLASH reliably stores memory
contents even after 10,000 erase and program cycles. The cell is
designed to optimize the erase and programming mechanisms. In
addition, the combination of advanced tunnel oxide processing and
low internal electric fields for erase and programming operations
produces reliable cycling.
Features
•FLASH EPROM internal program memory with Chip Erase
•Up to 64 k byte external program memory if the internal program
memory is disabled (EA
•Programmable security bits
•10,000 minimum erase/program cycles for each byte
•10 year minimum data retention
•Programming support available from many popular vendors
= 0)
89C51/89C52/89C54/89C58
OSCILLA T OR CHARACTERISTICS
XTAL1 and XTAL2 are the input and output, respectively, of an
inverting amplifier. The pins can be configured for use as an
on-chip oscillator.
To drive the device from an external clock source, XTAL1 should be
driven while XTAL2 is left unconnected. There are no requirements
on the duty cycle of the external clock signal, because the input to
the internal clock circuitry is through a divide-by-two flip-flop.
However, minimum and maximum high and low times specified in
the data sheet must be observed.
RESET
A reset is accomplished by holding the RST pin high for at least two
machine cycles (24 oscillator periods), while the oscillator is running.
To insure a good power-on reset, the RST pin must be high long
enough to allow the oscillator time to start up (normally a few
milliseconds) plus two machine cycles. At power-on, the voltage on
V
and RST must come up at the same time for a proper start-up.
CC
Ports 1, 2, and 3 will asynchronously be driven to their reset
condition when a voltage above V
The value on the EA
no further effect.
pin is latched when RST is deasserted and has
(min.) is applied to RST.
IH1
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
LOW POWER MODES
Stop Clock Mode
The static design enables the clock speed to be reduced down to
0 MHz (stopped). When the oscillator is stopped, the RAM and
Special Function Registers retain their values. This mode allows
step-by-step utilization and permits reduced system power
consumption by lowering the clock frequency down to any value. For
lowest power consumption the Power Down mode is suggested.
Idle Mode
In the idle mode (see Table 2), the CPU puts itself to sleep while all
of the on-chip peripherals stay active. The instruction to invoke the
idle mode is the last instruction executed in the normal operating
mode before the idle mode is activated. The CPU contents, the
on-chip RAM, and all of the special function registers remain intact
during this mode. The idle mode can be terminated either by any
enabled interrupt (at which time the process is picked up at the
interrupt service routine and continued), or by a hardware reset
which starts the processor in the same manner as a power-on reset.
Power-Down Mode
To save even more power, a Power Down mode (see Table 2) can
be invoked by software. In this mode, the oscillator is stopped and
the instruction that invoked Power Down is the last instruction
executed. The on-chip RAM and Special Function Registers retain
their values down to 2.0 V and care must be taken to return V
the minimum specified operating voltages before the Power Down
Mode is terminated.
Either a hardware reset or external interrupt can be used to exit from
Power Down. Reset redefines all the SFRs but does not change the
on-chip RAM. An external interrupt allows both the SFRs and the
on-chip RAM to retain their values.
To properly terminate Power Down the reset or external interrupt
should not be executed before V
operating level and must be held active long enough for the
oscillator to restart and stabilize (normally less than 10ms).
With an external interrupt, INT0 and INT1 must be enabled and
configured as level-sensitive. Holding the pin low restarts the oscillator
but bringing the pin back high completes the exit. Once the interrupt
is serviced, the next instruction to be executed after RETI will be the
one following the instruction that put the device into Power Down.
is restored to its normal
CC
Design Consideration
When the idle mode is terminated by a hardware reset, the device
normally resumes program execution, from where it left off, up to
CC
to
89C51/89C52/89C54/89C58
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 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.
ONCE Mode
The ONCE (“On-Circuit Emulation”) Mode facilitates testing and
debugging of systems without the device having to be removed from
the circuit. The ONCE Mode is invoked by:
1. Pull ALE low while the device is in reset and PSEN
2. Hold ALE low as RST is deactivated.
While the device is in ONCE Mode, the Port 0 pins go into a float
state, and the other port pins and ALE and PSEN
high. The oscillator circuit remains active. While the device is in this
mode, an emulator or test CPU can be used to drive the circuit.
Normal operation is restored when a normal reset is applied.
Programmable Clock-Out
A 50% duty cycle clock can be programmed to come out on P1.0.
This pin, besides being a regular I/O pin, has two alternate
functions. It can be programmed:
1. to input the external clock for Timer/Counter 2, or
2. to output a 50% duty cycle clock ranging from 61Hz to 4MHz at a
16MHz operating frequency.
To configure the Timer/Counter 2 as a clock generator, bit C/T
T2CON) must be cleared and bit T20E in T2MOD must be set. Bit
TR2 (T2CON.2) also must be set to start 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 this equation:
Oscillator Frequency
4 (65536 * RCAP2H,RCAP2L)
Where (RCAP2H,RCAP2L) = the content of RCAP2H and RCAP2L
taken as a 16-bit unsigned integer.
In the Clock-Out mode Timer 2 roll-overs will not generate an
interrupt. This is similar to when it 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 the
Clock-Out frequency will be the same.
is high;
are weakly pulled
2 (in
Table 2. External Pin Status During Idle and Power-Down Mode
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
TIMER 0 AND TIMER 1 OPERATION
Timer 0 and Timer 1
The “Timer” or “Counter” function is selected by control bits C/T in
the Special Function Register TMOD. These two Timer/Counters
have four operating modes, which are selected by bit-pairs (M1, M0)
in TMOD. Modes 0, 1, and 2 are the same for both Timers/Counters.
Mode 3 is different. The four operating modes are described in the
following text.
Mode 0
Putting either Timer into Mode 0 makes it look like an 8048 T imer,
which is an 8-bit Counter with a divide-by-32 prescaler. Figure 2
shows the Mode 0 operation as it applies to Timer 1.
In this mode, the Timer register is configured as a 13-bit register . As
the count rolls over from all 1s to all 0s, it sets the Timer interrupt
flag TF1. The counted input is enabled to the Timer when TR1 = 1
and either GA TE = 0 or INT1
Timer to be controlled by external input INT1
measurements). TR1 is a control bit in the Special Function Register
TCON (Figure 3). GATE is in TMOD.
The 13-bit register consists of all 8 bits of TH1 and the lower 5 bits
of TL1. The upper 3 bits of TL1 are indeterminate and should be
ignored. Setting the run flag (TR1) does not clear the registers.
Mode 0 operation is the same for the Timer 0 as for Timer 1.
Substitute TR0, TF0, and INT0
signals in Figure 2. There are two different GA TE bits, one for Timer
1 (TMOD.7) and one for Timer 0 (TMOD.3).
= 1. (Setting GATE = 1 allows the
, to facilitate pulse width
for the corresponding Timer 1
89C51/89C52/89C54/89C58
Mode 1
Mode 1 is the same as Mode 0, except that the Timer register is
being run with all 16 bits.
Mode 2
Mode 2 configures the Timer register as an 8-bit Counter (TL1) with
automatic reload, as shown in Figure 4. Overflow from TL1 not only
sets TF1, but also reloads TL1 with the contents of TH1, which is
preset by software. The reload leaves TH1 unchanged.
Mode 2 operation is the same for Timer/Counter 0.
Mode 3
Timer 1 in Mode 3 simply holds its count. The effect is the same as
setting TR1 = 0.
Timer 0 in Mode 3 establishes TL0 and TH0 as two separate
counters. The logic for Mode 3 on Timer 0 is shown in Figure 5. TL0
uses the Timer 0 control bits: C/T
the INT0
cycles) and takes over the use of TR1 and TF1 from Timer 1. Thus,
TH0 now controls the “Timer 1” interrupt.
Mode 3 is provided for applications requiring an extra 8-bit timer on
the counter. With Timer 0 in Mode 3, an 80C51 can look like it has
three Timer/Counters. When Timer 0 is in Mode 3, Timer 1 can be
turned on and off by switching it out of and into its own Mode 3, or
can still be used by the serial port as a baud rate generator, or in
fact, in any application not requiring an interrupt.
pin. TH0 is locked into a timer function (counting machine
, GATE, TR0, and TF0, as well as
TMODAddress = 89HReset Value = 00H
Not Bit Addressable
76543 2 1 0
GATEC/TM1
TIMER 1TIMER 0
GATEGating control when set. Timer/Counter “x” is enabled only while “INTx” pin is high and
“TRx” control pin is set. when cleared Timer “x” is enabled whenever “TRx” control bit is set.
C/TTimer or Counter Selector cleared for Timer operation (input from in=ternal system clock.)
Set for Counter operation (input from “Tx” input pin).
M1M0OPERATING
008048 Timer “TLx” serves as 5-bit prescaler.
0116-bit Timer/Counter “THx” and “TLx” are cascaded; there is no prescaler.
108-bit auto-reload Timer/Counter “THx” holds a value which is to be reloaded
into “TLx” each time it overflows.
11(Timer 0) TL0 is an 8-bit Timer/Counter controlled by the standard Timer 0 control bits.
TH0 is an 8-bit timer only controlled by Timer 1 control bits.
11(Timer 1) Timer/Counter 1 stopped.
Figure 1. Timer/Counter 0/1 Mode Control (TMOD) Register
M0GA TEC/T
M1M0
SU01514
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
TCON.7TF1Timer 1 overflow flag. Set by hardware on Timer/Counter overflow.
Cleared by hardware when processor vectors to interrupt routine, or clearing the bit in software.
TCON.6TR1Timer 1 Run control bit. Set/cleared by software to turn Timer/Counter on/off.
TCON.5TF0Timer 0 overflow flag. Set by hardware on Timer/Counter overflow.
Cleared by hardware when processor vectors to interrupt routine, or by clearing the bit in software.
TCON.4TR0Timer 0 Run control bit. Set/cleared by software to turn Timer/Counter on/off.
TCON.3IE1Interrupt 1 Edge flag. Set by hardware when external interrupt edge detected.
Cleared when interrupt processed.
TCON.2IT1Interrupt 1 type control bit. Set/cleared by software to specify falling edge/low level triggered
external interrupts.
TCON.1IE0Interrupt 0 Edge flag. Set by hardware when external interrupt edge detected.
Cleared when interrupt processed.
TCON.0IT0Interrupt 0 Type control bit. Set/cleared by software to specify falling edge/low level
triggered external interrupts.
Figure 3. Timer/Counter 0/1 Control (TCON) Register
SU01516
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Figure 5. Timer/Counter 0 Mode 3: Two 8-Bit Counters
TF1
Interrupt
SU01557
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
TIMER 2 OPERATION
Timer 2
Timer 2 is a 16-bit Timer/Counter which can operate as either an
event timer or an event counter, as selected by C/T
function register T2CON (see Figure 1). Timer 2 has three operating
modes: Capture, Auto-reload (up or down counting), and Baud Rate
Generator, which are selected by bits in the T2CON as shown in
Table 3.
Capture Mode
In the capture mode there are two options which are selected by bit
EXEN2 in T2CON. If EXEN2=0, then timer 2 is a 16-bit timer or
counter (as selected by C/T
sets bit TF2, the timer 2 overflow bit. This bit can be used to
generate an interrupt (by enabling the Timer 2 interrupt bit in the
IE register). If EXEN2= 1, Timer 2 operates as described above, but
with the added feature that a 1- to -0 transition at external input
T2EX causes the current value in the Timer 2 registers, TL2 and
TH2, to be captured into registers RCAP2L and RCAP2H,
respectively. In addition, the transition at T2EX causes bit EXF2 in
T2CON to be set, and EXF2 like TF2 can generate an interrupt
(which vectors to the same location as Timer 2 overflow interrupt.
The Timer 2 interrupt service routine can interrogate TF2 and EXF2
to determine which event caused the interrupt). The capture mode is
illustrated in Figure 2 (There is no reload value for TL2 and TH2 in
this mode. Even when a capture event occurs from T2EX, the
counter keeps on counting T2EX pin transitions or osc/12 pulses.).
2 in T2CON) which, upon overflowing
Auto-Reload Mode (Up or Down Counter)
In the 16-bit auto-reload mode, Timer 2 can be configured (as either
a timer or counter [C/T
or down. The counting direction is determined by bit DCEN (Down
Counter Enable) which is located in the T2MOD register (see
2 in T2CON]) then programmed to count up
2 in the special
89C51/89C52/89C54/89C58
Figure 3). When reset is applied the DCEN=0 which means Timer 2
will default to counting up. If DCEN bit is set, Timer 2 can count up
or down depending on the value of the T2EX pin.
Figure 4 shows Timer 2 which will count up automatically since
DCEN=0. In this mode there are two options selected by bit EXEN2
in T2CON register. If EXEN2=0, then T imer 2 counts up to 0FFFFH
and sets the TF2 (Overflow Flag) bit upon overflow. This causes the
Timer 2 registers to be reloaded with the 16-bit value in RCAP2L
and RCAP2H. The values in RCAP2L and RCAP2H are preset by
software means.
If EXEN2=1, then a 16-bit reload can be triggered either by an
overflow or by a 1-to-0 transition at input T2EX. This transition also
sets the EXF2 bit. The Timer 2 interrupt, if enabled, can be
generated when either TF2 or EXF2 are 1.
In Figure 5 DCEN=1 which enables Timer 2 to count up or down.
This mode allows pin T2EX to control the direction of count. When a
logic 1 is applied at pin T2EX Timer 2 will count up. Timer 2 will
overflow at 0FFFFH and set the TF2 flag, which can then generate
an interrupt, if the interrupt is enabled. This timer overflow also
causes the 16–bit value in RCAP2L and RCAP2H to be reloaded
into the timer registers TL2 and TH2.
When a logic 0 is applied at pin T2EX this causes Timer 2 to count
down. The timer will underflow when TL2 and TH2 become equal to
the value stored in RCAP2L and RCAP2H. Timer 2 underflow sets
the TF2 flag and causes 0FFFFH to be reloaded into the timer
registers TL2 and TH2.
The external flag EXF2 toggles when Timer 2 underflows or
overflows. This EXF2 bit can be used as a 17th bit of resolution if
needed. The EXF2 flag does not generate an interrupt in this mode
of operation.
T2CON Address = C8H
Bit Addressable
(MSB)(LSB)
SymbolPositionName and Significance
TF2T2CON.7Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set
EXF2T2CON.6Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX and
RCLKT2CON.5Receive clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock
TCLKT2CON.4Transmit clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its transmit clock
EXEN2T2CON.3Timer 2 external enable flag. When set, allows a capture or reload to occur as a result of a negative
TR2T2CON.2Start/stop control for Timer 2. A logic 1 starts the timer.
C/T
2T2CON.1Timer or counter select. (Timer 2)
CP/RL
2T2CON.0Capture/Reload flag. When set, captures will occur on negative transitions at T2EX if EXEN2 = 1. When
when either RCLK or TCLK = 1.
EXEN2 = 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).
in modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive clock.
in modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.
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.
cleared, auto-reloads will occur either with Timer 2 overflows or negative transitions at T2EX when
EXEN2 = 1. When either RCLK = 1 or TCLK = 1, this bit is ignored and the timer is forced to auto-reload
on Timer 2 overflow .
—Not implemented, reserved for future use1.
T2OETimer 2 Output Enable bit.
DCENDown Count Enable bit. When set, this allows Timer 2 to be configured as an up/down counter.
SU01559
1. User software should not write 1s to reserved bits. These bits may be used in future 8051 family products to invoke new features. In that
case, the reset or inactive value of the new bit will be 0, and its active value will be 1. The value read from a reserved bit is indeterminate.
Figure 3. Timer 2 Mode (T2MOD) Control Register
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
OSC
T2 PIN
T2EX PIN
÷ 12
TRANSITION
DETECTOR
C/T2 = 0
2 = 1
C/T
CONTROL
TR2
CONTROL
EXEN2
RELOAD
89C51/89C52/89C54/89C58
TL2
(8-BITS)
RCAP2LRCAP2H
TH2
(8-BITS)
TF2
EXF2
TIMER 2
INTERRUPT
SU00067
OSC
T2 PIN
÷12
C/T2 = 0
2 = 1
C/T
Figure 4. Timer 2 in Auto-Reload Mode (DCEN = 0)
(DOWN COUNTING RELOAD VALUE)
FFHFFH
OVERFLOW
TL2TH2
CONTROL
TR2
RCAP2LRCAP2H
(UP COUNTING RELOAD VALUE)T2EX PIN
Figure 5. Timer 2 Auto Reload Mode (DCEN = 1)
TOGGLE
COUNT
DIRECTION
1 = UP
0 = DOWN
TF2
EXF2
INTERRUPT
SU00730
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Philips SemiconductorsProduct data
Baud Rate
Osc Freq
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
NOTE: OSC. Freq. is divided by 2, not 12.
OSC
T2 Pin
T2EX Pin
÷ 2
Transition
Detector
C/T2 = 0
C/T
2 = 1
Control
TR2
EXF2
TL2
(8-bits)
RCAP2LRCAP2H
Timer 2
Interrupt
TH2
(8-bits)
89C51/89C52/89C54/89C58
Timer 1
Overflow
÷ 2
“0”“1”
SMOD
RCLK
÷ 16
÷ 16TX Clock
RX Clock
TCLK
Reload
“0”“1”
“0”“1”
Control
EXEN2
Note availability of additional external interrupt.
Bits TCLK and/or RCLK in T2CON (Table 4) allow the serial port
transmit and receive baud rates to be derived from either Timer 1 or
Timer 2. When TCLK= 0, Timer 1 is used as the serial port transmit
baud rate generator . When TCLK= 1, Timer 2 is used as the serial
port transmit baud rate generator. RCLK has the same effect for the
serial port receive baud rate. With these two bits, the serial port can
have different receive and transmit baud rates – one generated by
Timer 1, the other by Timer 2.
Figure 6 shows the Timer 2 in baud rate generation mode. The baud
rate generation mode is like 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.
SU00068
The baud rates in modes 1 and 3 are determined by Timer 2’s
overflow rate given below:
Modes 1 and 3 Baud Rates +
Timer 2 Overflow Rate
16
The timer can be configured for either “timer” or “counter” operation.
In many applications, it is configured for “timer” operation (C/T
2*=0).
Timer operation is different for Timer 2 when it is being used as a
baud rate generator.
Usually, as a timer it would increment every machine cycle (i.e., 1/12
the oscillator frequency). As a baud rate generator, it increments
every state time (i.e., 1/2 the oscillator frequency). Thus the baud
rate formula is as follows:
Modes 1 and 3 Baud Rates =
Oscillator Frequency
[32 [65536 * (RCAP2H,RCAP2L)]]
Where: (RCAP2H, RCAP2L) = The content of RCAP2H and
RCAP2L taken as a 16-bit unsigned integer.
The Timer 2 as a baud rate generator mode shown in Figure 6, is
valid only if RCLK and/or TCLK = 1 in T2CON register. Note that a
rollover in TH2 does not set TF2, and will not generate an interrupt.
Thus, the Timer 2 interrupt does not have to be disabled when
Timer 2 is in the baud rate generator mode. Also if the EXEN2
(T2 external enable flag) is set, a 1-to-0 transition in T2EX
(Timer/counter 2 trigger input) will set EXF2 (T2 external flag) but
will not cause a reload from (RCAP2H, RCAP2L) to (TH2,TL2).
Therefore when Timer 2 is in use as a baud rate generator, T2EX
can be used as an additional external interrupt, if needed.
2002 Jan 15
17
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
When Timer 2 is in the baud rate generator mode, one should not try
to read or write TH2 and TL2. As a baud rate generator, T imer 2 is
incremented every state time (osc/2) or asynchronously from pin T2;
under these conditions, a read or write of TH2 or TL2 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.
Table 4 shows commonly used baud rates and how they can be
obtained from Timer 2.
Summary Of Baud Rate Equations
Timer 2 is in baud rate generating mode. If Timer 2 is being clocked
through pin T2(P1.0) the baud rate is:
Baud Rate +
Timer 2 Overflow Rate
16
Table 5. Timer 2 as a Timer
MODE
16-bit Auto-Reload00H08H
16-bit Capture01H09H
Baud rate generator receive and transmit same baud rate34H36H
Receive only24H26H
Transmit only14H16H
If Timer 2 is being clocked internally , the baud rate is:
Baud Rate +
Where f
To obtain the reload value for RCAP2H and RCAP2L, the above
equation can be rewritten as:
RCAP2H,RCAP2L + 65536 *
Timer/Counter 2 Set-up
Except for the baud rate generator mode, the values given for T2CON
do not include the setting of the TR2 bit. Therefore, bit TR2 must be
set, separately, to turn the timer on. see Table 5 for set-up of Timer 2
as a timer. Also see Table 6 for set-up of Timer 2 as a counter.
INTERNAL CONTROL
89C51/89C52/89C54/89C58
f
[32 [65536 * (RCAP2H,RCAP2L)]]
= Oscillator Frequency
OSC
(Note 1)
T2CON
OSC
f
ǒ
32 Baud Rate
EXTERNAL CONTROL
OSC
(Note 2)
Ǔ
Table 6. Timer 2 as a Counter
TMOD
MODE
16-bit02H0AH
Auto-Reload03H0BH
NOTES:
1. Capture/reload occurs only on timer/counter overflow.
2. Capture/reload occurs on timer/counter overflow and a 1-to-0 transition on T2EX (P1.1) pin except when Timer 2 is used in the baud rate
generator mode.
INTERNAL CONTROL
(Note 1)
EXTERNAL CONTROL
(Note 2)
2002 Jan 15
18
Page 19
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Enhanced UART operation
In addition to the standard operation modes, the UART can perform
framing error detect by looking for missing stop bits, and automatic
address recognition. The UART also fully supports multiprocessor
communication.
When used for framing error detect the UART looks for missing stop
bits in the communication. A missing bit will set the FE bit in the
SCON register. The FE bit shares the SCON.7 bit with SM0 and the
function of SCON.7 is determined by PCON.6 (SMOD0) (see
Figure 7). If SMOD0 is set then SCON.7 functions as FE. SCON.7
functions as SM0 when SMOD0 is cleared. When used as FE
SCON.7 can only be cleared by software. Refer to Figure 8.
Automatic Address Recognition
Automatic Address Recognition is a feature which allows the UART
to recognize certain addresses in the serial bit stream by using
hardware to make the comparisons. This feature saves a great deal
of software overhead by eliminating the need for the software to
examine every serial address which passes by the serial port. This
feature is enabled by setting the SM2 bit in SCON. In the 9 bit UART
modes, mode 2 and mode 3, the Receive Interrupt flag (RI) will be
automatically set when the received byte contains either the “Given”
address or the “Broadcast” address. The 9 bit mode requires that
the 9th information bit is a 1 to indicate that the received information
is an address and not data. Automatic address recognition is shown
in Figure 9.
The 8 bit mode is called Mode 1. In this mode the RI flag will be set
if SM2 is enabled and the information received has a valid stop bit
following the 8 address bits and the information is either a Given or
Broadcast address.
Mode 0 is the Shift Register mode and SM2 is ignored.
Using the Automatic Address Recognition feature allows a master to
selectively communicate with one or more slaves by invoking the
Given slave address or addresses. All of the slaves may be
contacted by using the Broadcast address. Two special Function
Registers are used to define the slave’s address, SADDR, and the
address mask, SADEN. SADEN is used to define which bits in the
SADDR are to be used and which bits are “don’t care”. The SADEN
mask can be logically ANDed with the SADDR to create the “Given”
address which the master will use for addressing each of the slaves.
Use of the Given address allows multiple slaves to be recognized
while excluding others. The following examples will help to show the
versatility of this scheme:
Slave 0SADDR = 1100 0000
SADEN = 1111 1101
Given=1100 00X0
89C51/89C52/89C54/89C58
Slave 1SADDR = 1100 0000
SADEN = 1111 1110
Given=1100 000X
In the above example SADDR is the same and the SADEN data is
used to differentiate between the two slaves. Slave 0 requires a 0 in
bit 0 and it ignores bit 1. Slave 1 requires a 0 in bit 1 and bit 0 is
ignored. A unique address for Slave 0 would be 1100 0010 since
slave 1 requires a 0 in bit 1. A unique address for slave 1 would be
1100 0001 since a 1 in bit 0 will exclude slave 0. Both slaves can be
selected at the same time by an address which has bit 0 = 0 (for
slave 0) and bit 1 = 0 (for slave 1). Thus, both could be addressed
with 1100 0000.
In a more complex system the following could be used to select
slaves 1 and 2 while excluding slave 0:
Slave 0SADDR = 1100 0000
SADEN = 1111 1001
Given=1 100 0XX0
Slave 1SADDR = 1110 0000
SADEN = 1111 1010
Given=1 110 0X0X
Slave 2SADDR = 1110 0000
SADEN = 1111 1100
Given=1110 00XX
In the above example the differentiation among the 3 slaves is in the
lower 3 address bits. Slave 0 requires that bit 0 = 0 and it can be
uniquely addressed by 1110 01 10. Slave 1 requires that bit 1 = 0 and
it can be uniquely addressed by 1110 and 0101. Slave 2 requires
that bit 2 = 0 and its unique address is 1110 0011. To select Slaves 0
and 1 and exclude Slave 2 use address 1110 0100, since it is
necessary to make bit 2 = 1 to exclude slave 2.
The Broadcast Address for each slave is created by taking the
logical OR of SADDR and SADEN. Zeros in this result are trended
as don’t-cares. In most cases, interpreting the don’t-cares as ones,
the broadcast address will be FF hexadecimal.
Upon reset SADDR (SFR address 0A9H) and SADEN (SFR
address 0B9H) are leaded with 0s. This produces a given address
of all “don’t cares” as well as a Broadcast address of all “don’t
cares”. This effectively disables the Automatic Addressing mode and
allows the microcontroller to use standard 80C51 type UART drivers
which do not make use of this feature.
2002 Jan 15
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Page 20
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
SCON Address = 98H
Bit Addressable
76543210
SM0/FESM1SM2RENTB8RB8TlRl
(SMOD0 = 0/1)*
SymbolPositionFunction
FESCON.7Framing Error bit. This bit is set by the receiver when an invalid stop bit is detected. The FE bit is not
SM0SCON.7Serial Port Mode Bit 0, (SMOD0 must = 0 to access bit SM0)
SM1SCON.6Serial Port Mode Bit 1
SM2SCON.5Enables the Automatic Address Recognition feature in Modes 2 or 3. If SM2 = 1 then Rl will not be set
RENSCON.4Enables serial reception. Set by software to enable reception. Clear by software to disable reception.
TB8SCON.3The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired.
RB8SCON.2In modes 2 and 3, the 9th data bit that was received. In Mode 1, if SM2 = 0, RB8 is the stop bit that
TlSCON.1Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or at the beginning of
Rl SCON.0Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or halfway through the
NOTES:
*SMOD0 is located at PCON.6.
= oscillator frequency
**f
OSC
cleared by valid frames but should be cleared by software. The SMOD0 bit must be set to enable
access to the FE bit.*
unless the received 9th data bit (RB8) is 1, indicating an address, and the received byte is a Given or
Broadcast Address. In Mode 1, if SM2 = 1 then Rl will not be activated unless a valid stop bit was
received, and the received byte is a Given or Broadcast Address. In Mode 0, SM2 should be 0.
was received.
In Mode 0, RB8 is not used.
the stop bit in the other modes, in any serial transmission. Must be cleared by software.
stop bit time in the other modes, in any serial reception (except see SM2). Must be cleared by
software.
89C51/89C52/89C54/89C58
Reset Value = 0000 0000B
OSC
OSC
/12 or f
/64 or f
/6 depending on the mode
OSC
/32
OSC
SU01484
2002 Jan 15
Figure 7. SCON: Serial Port Control Register
20
Page 21
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
D0D1D2D3D4D5D6D7D8
START
BIT
SM0 / FESM1SM2RENTB8RB8TIRI
SMOD1SMOD0–POFGF1GF0PDIDL
0 : SCON.7 = SM0
1 : SCON.7 = FE
Figure 8. UART Framing Error Detection
89C51/89C52/89C54/89C58
DATA BYTE
SET FE BIT IF STOP BIT IS 0 (FRAMING ERROR)
SM0 TO UART MODE CONTROL
ONLY IN
MODE 2, 3
SCON
(98H)
PCON
(87H)
STOP
BIT
SU01191
D0D1D2D3D4D5D6D7D8
SM0SM1SM2RENTB8RB8TIRI
1
1
RECEIVED ADDRESS D0 TO D7
PROGRAMMED ADDRESS
IN UART MODE 2 OR MODE 3 AND SM2 = 1:
INTERRUPT IF REN=1, RB8=1 AND “RECEIVED ADDRESS” = “PROGRAMMED ADDRESS”
– WHEN OWN ADDRESS RECEIVED, CLEAR SM2 TO RECEIVE DATA BYTES
– WHEN ALL DATA BYTES HAVE BEEN RECEIVED: SET SM2 TO WAIT FOR NEXT ADDRESS.
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Interrupt Priority Structure
0
INT0IT0
1
TF0
0
INT1
TF1
TI
RI
TF2, EXF2
IT1
1
Figure 10. 80C51 Interrupt Sources
Interrupts
The devices described in this data sheet provide six interrupt
sources. These are shown in Figure 10. The External Interrupts
INT0
and INT1 can each be either level-activated or
transition-activated, depending on bits IT0 and IT1 in Register
TCON. The flags that actually generate these interrupts are bits IE0
and IE1 in TCON. When an external interrupt is generated, the flag
that generated it is cleared by the hardware when the service routine
is vectored to only if the interrupt was transition-activated. If the
interrupt was level-activated, then the external requesting source is
what controls the request flag, rather than the on-chip hardware.
The Timer 0 and Timer 1 Interrupts are generated by TF0 and TF1,
which are set by a rollover in their respective Timer/Counter
registers (except see Timer 0 in Mode 3). When a timer interrupt is
generated, the flag that generated it is cleared by the on-chip
hardware when the service routine is vectored to.
The Serial Port Interrupt is generated by the logical OR of RI and TI.
Neither of these flags is cleared by hardware when the service
routine is vectored to. In fact, the service routine will normally have
to determine whether it was RI or TI that generated the interrupt,
and the bit will have to be cleared in software.
All of the bits that generate interrupts can be set or cleared by
software, with the same result as though it had been set or cleared
by hardware. That is, interrupts can be generated or pending
interrupts can be canceled in software.
Each of these interrupt sources can be individually enabled or
disabled by setting or clearing a bit in Special Function Register IE
(Figure 11). IE also contains a global disable bit, EA
all interrupts at once.
IE0
IE1
Interrupt
Sources
SU01521
, which disables
89C51/89C52/89C54/89C58
Priority Level Structure
Each interrupt source can also be individually programmed to one of
four priority levels by setting or clearing bits in Special Function
Registers IP (Figure 12) and IPH (Figure 13). A lower-priority
interrupt can itself be interrupted by a higher-priority interrupt, but
not by another interrupt of the same level. A high-priority level 3
interrupt can’t be interrupted by any other interrupt source.
If two request of different priority levels are received simultaneously,
the request of higher priority level is serviced. If requests of the
same priority level are received simultaneously, an internal polling
sequence determines which request is serviced. Thus within each
priority level there is a second priority structure determined by the
polling sequence as follows:
SourcePriority Within Level
1. IE0 (External Int 0)(highest)
2. TF0 (Timer 0)
3. IE1 (External Int 1)
4. TF1 (Timer 1)
5. RI+TI (UART)
6. TF2, EXF2 (Timer 2)(lowest)
Note that the “priority within level” structure is only used to resolve
simultaneous requests of the same priority level.
The IP and IPH registers contain a number of unimplemented bits.
User software should not write 1s to these positions, since they may
be used in other 80C51 Family products.
How Interrupts Are Handled
The interrupt flags are sampled at S5P2 of every machine cycle.
The samples are polled during the following machine cycle. If one of
the flags was in a set condition at S5P2 of the preceding cycle, the
polling cycle will find it and the interrupt system will generate an
LCALL to the appropriate service routine, provided this
hardware-generated LCALL is not blocked by any of the following
conditions:
1. An interrupt of equal or higher priority level is already in
progress.
2. The current (polling) cycle is not the final cycle in the execution
of the instruction in progress.
3. The instruction in progress is RETI or any write to the IE or IP
registers.
Any of these three conditions will block the generation of the LCALL
to the interrupt service routine. Condition 2 ensures that the
instruction in progress will be completed before vectoring to any
service routine. Condition 3 ensures that if the instruction in
progress is RETI or any access to IE or IP, then at least one more
instruction will be executed before any interrupt is vectored to.
The polling cycle is repeated with each machine cycle, and the
values polled are the values that were present at S5P2 of the
previous machine cycle. Note that if an interrupt flag is active but not
being responded to for one of the above conditions, if the flag is not
still active when the blocking condition is removed, the denied
interrupt will not be serviced. In other words, the fact that the
interrupt flag was once active but not serviced is not remembered.
Every polling cycle is new.
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
IEAddress = 0A8H
Bit Addressable
Enable Bit = 1 enables the interrupt.
Enable Bit = 0 disables it.
BITSYMBOLFUNCTION
IE.7EAGlobal disable bit. If EA = 0, all interrupts are disabled. If EA = 1, each interrupt can be individually
enabled or disabled by setting or clearing its enable bit.
IE.6—Not implemented. Reserved for future use.
IE.5ET2Timer 2 interrupt enable bit.
IE.4ESSerial Port interrupt enable bit.
IE.3ET1Timer 1 interrupt enable bit.
IE.2EX1External interrupt 1 enable bit.
IE.1ET0Timer 0 interrupt enable bit.
IE.0EX0External interrupt 0 enable bit.
Figure 11. Interrupt Enable (IE) Register
89C51/89C52/89C54/89C58
Reset Value = 0X000000B
01234567
ET0EX1ET1ESET2—EA
EX0
SU01522
IPAddress = 0B8H
Bit Addressable
Priority Bit = 1 assigns higher priority
Priority Bit = 0 assigns lower priority
Priority Bit = 1 assigns higher priority
Priority Bit = 0 assigns lower priority
BITSYMBOLFUNCTION
IPH.7—Not implemented, reserved for future use.
IPH.6—Not implemented, reserved for future use.
IPH.5PT2HTimer 2 interrupt priority bit high.
IPH.4PSHSerial Port interrupt priority bit high.
IPH.3PT1HTimer 1 interrupt priority bit high.
IPH.2PX1HExternal interrupt 1 priority bit high.
IPH.1PT0HTimer 0 interrupt priority bit high.
IPH.0PX0HExternal interrupt 0 priority bit high.
Reset Value = xx000000B
01234567
PT0PX1PT1PSPT2——
PT0HPX1HPT1HPSHPT2H——
PX0
SU01523
Reset Value = xx000000B
01234567
PX0H
SU01524
2002 Jan 15
Figure 13. Interrupt Priority HIGH (IPH) Register
23
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Philips SemiconductorsProduct data
INTERRUPT PRIORITY LEVEL
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
. . . . . . . . .
ε
Interrupt
Latched
S5P2S6
Interrupt
Goes
Active
. . . . . . . . .
The polling cycle/LCALL sequence is illustrated in Figure 14.
Note that if an interrupt of higher priority level goes active prior to
S5P2 of the machine cycle labeled C3 in Figure 14, then in
accordance with the above rules it will be vectored to during C5 and
C6, without any instruction of the lower priority routine having been
executed.
Thus the processor acknowledges an interrupt request by executing
a hardware-generated LCALL to the appropriate servicing routine. In
some cases it also clears the flag that generated the interrupt, and in
other cases it doesn’t. It never clears the Serial Port flag. This has to
be done in the user’s software. It clears an external interrupt flag
(IE0 or IE1) only if it was transition-activated. The
hardware-generated LCALL pushes the contents of the Program
Counter on to the stack (but it does not save the PSW) and reloads
the PC with an address that depends on the source of the interrupt
being vectored to, as shown in Table 7.
Execution proceeds from that location until the RETI instruction is
encountered. The RETI instruction informs the processor that this
interrupt routine is no longer in progress, then pops the top two
bytes from the stack and reloads the Program Counter. Execution of
the interrupted program continues from where it left off.
Note that a simple RET instruction would also have returned
execution to the interrupted program, but it would have left the
interrupt control system thinking an interrupt was still in progress,
making future interrupts impossible.
External Interrupts
The external sources can be programmed to be level-activated or
transition-activated by setting or clearing bit IT1 or IT0 in Register
TCON. If ITx = 0, external interrupt x is triggered by a detected low
at the INT
x pin. If ITx = 1, external interrupt x is edge triggered. In
this mode if successive samples of the INT
cycle and a low in the next cycle, interrupt request flag IEx in TCON
is set. Flag bit IEx then requests the interrupt.
Since the external interrupt pins are sampled once each machine
cycle, an input high or low should hold for at least 12 oscillator
periods to ensure sampling. If the external interrupt is
transition-activated, the external source has to hold the request pin
high for at least one cycle, and then hold it low for at least one cycle.
This is done to ensure that the transition is seen so that interrupt
request flag IEx will be set. IEx will be automatically cleared by the
CPU when the service routine is called.
If the external interrupt is level-activated, the external source has to
hold the request active until the requested interrupt is actually
generated. Then it has to deactivate the request before the interrupt
C1C2C3C4C5
Interrupts
Are Polled
This is the fastest possible response when C2 is the final cycle of an instruction other than RETI or an access to IE or IP.
Figure 14. Interrupt Response Timing Diagram
x pin show a high in one
89C51/89C52/89C54/89C58
. . . .
. . . .
. . . .
Long Call to
Interrupt
Vector Address
service routine is completed, or else another interrupt will be
generated.
Response Time
The INT0
and INT1 levels are inverted and latched into IE0 and IE1
at S5P2 of every machine cycle. The values are not actually polled
by the circuitry until the next machine cycle. If a request is active
and conditions are right for it to be acknowledged, a hardware
subroutine call to the requested service routine will be the next
instruction to be executed. The call itself takes two cycles. Thus, a
minimum of three complete machine cycles elapse between
activation of an external interrupt request and the beginning of
execution of the first instruction of the service routine. Figure 14
shows interrupt response timings.
A longer response time would result if the request is blocked by one
of the 3 previously listed conditions. If an interrupt of equal or higher
priority level is already in progress, the additional wait time obviously
depends on the nature of the other interrupt’s service routine. If the
instruction in progress is not in its final cycle, the additional wait time
cannot be more the 3 cycles, since the longest instructions (MUL
and DIV) are only 4 cycles long, and if the instruction in progress is
RETI or an access to IE or IP, the additional wait time cannot be
more than 5 cycles (a maximum of one more cycle to complete the
instruction in progress, plus 4 cycles to complete the next instruction
if the instruction is MUL or DIV).
Thus, in a single-interrupt system, the response time is always more
than 3 cycles and less than 9 cycles.
As previously mentioned, the derivatives described in this data
sheet have a four-level interrupt structure. The corresponding
registers are IE, IP and IPH. (See Figures 11, 12, and 13.) The IPH
(Interrupt Priority High) register makes the four-level interrupt
structure possible.
The function of the IPH SFR is simple and when combined with the
IP SFR determines the priority of each interrupt. The priority of each
interrupt is determined as shown in the following table:
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
An interrupt will be serviced as long as an interrupt of equal or
higher priority is not already being serviced. If an interrupt of equal
or higher level priority is being serviced, the new interrupt will wait
until it is finished before being serviced. If a lower priority level
The AO bit (AUXR.0) in the AUXR register when set disables the ALE output, unless the CPU needs to perform an off-chip memory access.
interrupt is being serviced, it will be stopped and the new interrupt
serviced. When the new interrupt is finished, the lower priority level
interrupt that was stopped will be completed.
89C51/89C52/89C54/89C58
2
03H
AUXR
SymbolFunction
AODisable/Enable ALE
—Not implemented, reserved for future use
1. User software should not write 1s to reserved bits. These bits may be used in future 8051 family products to invoke new features. In that
case, the reset or inactive value of the new bit will be 0, and its active value will be 1. The value read from a reserved bit is indeterminate.
Address = 8EH
Not Bit Addressable
76543210
———————AO
AOOperating Mode
0ALE is emitted at a constant rate of
1ALE is active only during off-chip memory accesses.
1
.
Figure 15. AUXR: Auxiliary Register
1
/3 the oscillator frequency (6 clock mode; 1/6 f
Reset Value = xxxx xxx0B
in 12 clock mode)
OSC
SU01560
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Dual DPTR
The dual DPTR structure (see Figure 17) is a way by which the chip
will specify the address of an external data memory location. There
are two 16-bit DPTR registers that address the external memory,
and a single bit called DPS = AUXR1/bit0 that allows the program
code to switch between them.
AUXR1
SymbolFunction
GF2The GF2 bit is a general purpose user-defined flag. Note that bit 2 is not writable and is always read as a zero. This
DPSDPS = AUXR1/bit0 = Switches between DPTR0 and DPTR1.
—Not implemented, reserved for future use
1. User software should not write 1s to reserved bits. These bits may be used in future 8051 family products to invoke new features. In that
case, the reset or inactive value of the new bit will be 0, and its active value will be 1. The value read from a reserved bit is indeterminate.
Address = A2H
Not Bit Addressable
76543210
————GF20—DPS
allows the DPS bit to be quickly toggled simply by executing an INC AUXR1 instruction without affecting the GF2 bit.
Select RegDPS
DPTR00
DPTR11
1
.
Figure 16. AUXR1: Auxiliary 1 Register
•New Register Name: AUXR1#
•SFR Address: A2H
•Reset Value: xxxx00x0B
89C51/89C52/89C54/89C58
Reset Value = xxxx 00x0B
SU01561
DPS
BIT0
AUXR1
DPH
(83H)
Figure 17.
DPTR Instructions
The instructions that refer to DPTR refer to the data pointer that is
currently selected using the AUXR1/bit 0 register. The six
instructions that use the DPTR are as follows:
DPL
(82H)
DPTR1
DPTR0
EXTERNAL
DATA
MEMORY
SU00745A
INC DPTRIncrements the data pointer by 1
MOV DPTR, #data16Loads the DPTR with a 16-bit constant
MOV A, @ A+DPTRMove code byte relative to DPTR to ACC
MOVX A, @ DPTRMove external RAM (16-bit address) to
ACC
MOVX @ DPTR , AMove ACC to external RAM (16-bit
address)
JMP @ A + DPTRJump indirect relative to DPTR
The data pointer can be accessed on a byte-by-byte basis by
specifying the low or high byte in an instruction which accesses the
SFRs. See application note AN458 for more details.
2002 Jan 15
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
ABSOLUTE MAXIMUM RATINGS
Operating temperature under bias0 to +70 or –40 to +85°C
Storage temperature range–65 to +150°C
Voltage on EA/VPP pin to V
Voltage on any other pin to V
Maximum IOL per I/O pin15mA
Power dissipation (based on package heat transfer limitations, not device power consumption)1.5W
NOTES:
1. Stresses above 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 conditions other than those described in the AC and DC Electrical Characteristics section
of this specification is not implied.
2. This product includes circuitry specifically designed for the protection of its internal devices from the damaging effects of excessive static
charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying greater than the rated maximum.
3. Parameters are valid over operating temperature range unless otherwise specified. All voltages are with respect to VSS unless otherwise noted.
SS
SS
AC ELECTRICAL CHARACTERISTICS
T
= 0°C to +70°C or –40°C to +85°C
amb
SYMBOL
1/t
CLCL
Oscillator frequency033MHz
1, 2, 3
PARAMETER
PARAMETER
89C51/89C52/89C54/89C58
RATINGUNIT
0 to +13.0V
–0.5 to +6.5V
CLOCK FREQUENCY
RANGE –f
MINMAX
UNIT
2002 Jan 15
27
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Philips SemiconductorsProduct data
SYMBOL
PARAMETER
UNIT
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
DC ELECTRICAL CHARACTERISTICS
T
= 0°C to +70°C or –40°C to +85°C; 5 V ±10%; VSS = 0 V
amb
TEST
CONDITIONS
V
IL
V
IH
V
IH1
V
OL
V
OL1
V
OH
V
OH1
I
IL
I
TL
I
LI
I
CC
R
RST
C
IO
NOTES:
1. Typical ratings are not guaranteed. The values listed are at room temperature, 5 V.
2. Capacitive loading on ports 0 and 2 may cause spurious noise to be superimposed on the V
to external bus capacitance discharging into the port 0 and port 2 pins when these pins make 1-to-0 transitions during bus operations. In the
worst cases (capacitive loading > 100pF), the noise pulse on the ALE pin may exceed 0.8V . In such cases, it may be desirable to qualify
ALE with a Schmitt Trigger, or use an address latch with a Schmitt Trigger STROBE input. I
single output sinks more than 5 mA and no more than two outputs exceed the test conditions.
3. Capacitive loading on ports 0 and 2 may cause the V
address bits are stabilizing.
4. Pins of ports 1, 2 and 3 source a transition current when they are being externally driven from 1 to 0. The transition current reaches its
maximum value when V
5. See Figures 26 through 29 for I
6. This value applies to T
7. Load capacitance for port 0, ALE, and PSEN
8. Under steady state (non-transient) conditions, I
If I
test conditions.
9. ALE is tested to V
10.Pin capacitance is characterized but not tested. Pin capacitance is less than 25 pF. Pin capacitance of ceramic package is less than 15 pF
(except EA
Input low voltage4.5 V < VCC < 5.5 V–0.50.2 VCC–0.1V
Input high voltage (ports 0, 1, 2, 3, EA)0.2 VCC+0.9VCC+0.5V
Input high voltage, XTAL1, RST0.7 V
Output low voltage, ports 1, 2, 3
Output low voltage, port 0, ALE, PSEN
Output high voltage, ports 1, 2, 3
Output high voltage (port 0 in external bus mode),
on ALE and PSEN to momentarily fall below the VCC–0.7 specification when the
OH
is approximately 2 V.
IN
Active mode:I
Idle mode:I
Maximum I
Maximum I
Maximum total I
exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed
OL
CC(MAX)
CC(MAX)
amb
per port pin:15 mA (*NOTE: This is 85°C specification.)
OL
per 8-bit port:26 mA
OL
for all outputs:71 mA
OL
, except when ALE is off then VOH is the voltage specification.
OH1
test conditions and Figure 25 for I
CC
= (0.56 × FREQ. + 8.0)mA
= (0.30 × FREQ. +2.0)mA
= 0°C to +70°C.
= 100pF, load capacitance for all other outputs = 80 pF.
OL
must be externally limited as follows:
vs Freq.
CC
is 25 pF).
89C51/89C52/89C54/89C58
LIMITS
MINTYP
CC
2
2
VCC – 0.7V
VCC – 0.7V
s of ALE and ports 1 and 3. The noise is due
OL
can exceed these conditions provided that no
OL
1
MAX
VCC+0.5V
0.4V
0.4V
–650µA
2002 Jan 15
28
Page 29
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
AC ELECTRICAL CHARACTERISTICS
T
= 0°C to +70°C or –40°C to +85°C, VCC = 5 V ±10%, VSS = 0V
amb
SYMBOLFIGUREPARAMETERMINMAXMINMAXUNIT
1/t
CLCL
t
LHLL
t
AVLL
t
LLAX
t
LLIV
t
LLPL
t
PLPH
t
PLIV
t
PXIX
t
PXIZ
t
AVIV
t
PLAZ
Data Memory
t
RLRH
t
WLWH
t
RLDV
t
RHDX
t
RHDZ
t
LLDV
t
AVDV
t
LLWL
t
AVWL
t
QVWX
t
WHQX
t
QVWH
t
RLAZ
t
WHLH
External Clock
t
CHCX
t
CLCX
t
CLCH
t
CHCL
Shift Register
t
XLXL
t
QVXH
t
XHQX
t
XHDX
t
XHDV
NOTES:
1. Parameters are valid over operating temperature range unless otherwise specified.
2. Load capacitance for port 0, ALE, and PSEN
3. Interfacing the microcontroller to devices with float times up to 45 ns is permitted. This limited bus contention will not cause damage to Port 0 drivers.
4. Parts are guaranteed to operate down to 0 Hz.
18Oscillator frequency
Speed versions
18ALE pulse width2t
18Address valid to ALE lowt
18Address hold after ALE lowt
18ALE low to valid instruction in4t
18ALE low to PSEN lowt
18PSEN pulse width3t
18PSEN low to valid instruction in3t
18Input instruction hold after PSEN00ns
18Input instruction float after PSENt
18Address to valid instruction in5t
18PSEN low to address float1010ns
19, 20RD pulse width6t
19, 20WR pulse width6t
19, 20RD low to valid data in5t
19, 20Data hold after RD00ns
19, 20Data float after RD2t
19, 20ALE low to valid data in8t
19, 20Address to valid data in9t
19, 20ALE low to RD or WR low3t
19, 20Address valid to WR low or RD low4t
19, 20Data valid to WR transitiont
19, 20Data hold after WRt
20Data valid to WR high7t
19, 20RD low to address float00ns
19, 20RD or WR high to ALE hight
21Serial port clock cycle time12t
21Output data setup to clock rising edge10t
21Output data hold after clock rising edge2t
21Input data hold after clock rising edge00ns
21Clock rising edge to input data valid10t
= 100 pF, load capacitance for all other outputs = 80 pF.
1, 2, 3
VARIABLE CLOCK
3.533
–4021ns
CLCL
–255ns
CLCL
–255ns
CLCL
–255ns
CLCL
–4545ns
CLCL
–10082ns
CLCL
–10082ns
CLCL
–503t
CLCL
–7545ns
CLCL
–300ns
CLCL
–255ns
CLCL
–13080ns
CLCL
–25t
CLCL
CLCL
–133167ns
CLCL
–8050ns
CLCL
89C51/89C52/89C54/89C58
4
–6555ns
CLCL
–6030ns
CLCL
–255ns
CLCL
–8070ns
CLCL
–9060ns
CLCL
–2832ns
CLCL
–15090ns
CLCL
–165105ns
CLCL
+5040140ns
CLCL
+25555ns
CLCL
CLCL–tCLCX
CLCL–tCHCX
–133167ns
CLCL
33MHz CLOCK
3.533
MHz
ns
ns
360ns
2002 Jan 15
29
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Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
EXPLANATION OF THE AC SYMBOLS
Each timing symbol has five characters. The first character is always
‘t’ (= time). The other characters, depending on their positions,
indicate the name of a signal or the logical status of that signal. The
designations are:
A – Address
C – Clock
D – Input data
H – Logic level high
I – Instruction (program memory contents)
L – Logic level low, or ALE
t
ALE
PSEN
PORT 0
LHLL
t
t
AVLL
LLPL
t
LLAX
A0–A7A0–A7
t
LLIV
t
PLIV
t
t
PLAZ
PLPH
t
PXIX
89C51/89C52/89C54/89C58
P – PSEN
Q – Output data
R–RD
signal
t – Time
V – Valid
W– WR
X – No longer a valid logic level
Z – Float
Examples: t
INSTR IN
t
PXIZ
signal
= Time for address valid to ALE low.
AVLL
t
LLPL
=Time for ALE low to PSEN low.
ALE
PSEN
PORT 0
PORT 2
RD
PORT 2
t
AVLL
t
LLAX
A0–A7
FROM RI OR DPL
t
AVWL
t
AVIV
A0–A15A8–A15
Figure 18. External Program Memory Read Cycle
t
WHLH
t
LLDV
t
LLWL
t
RLAZ
t
AVDV
P2.0–P2.7 OR A8–A15 FROM DPFA0–A15 FROM PCH
t
RLDV
t
RLRH
t
RHDZ
t
RHDX
DATA INA0–A7 FROM PCLINSTR IN
SU00006
2002 Jan 15
SU00025
Figure 19. External Data Memory Read Cycle
30
Page 31
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
ALE
PSEN
t
LLWL
WR
t
LLAX
A0–A7
FROM RI OR DPL
t
AVWL
t
QVWX
P2.0–P2.7 OR A8–A15 FROM DPFA0–A15 FROM PCH
PORT 0
PORT 2
t
AVLL
89C51/89C52/89C54/89C58
t
WHLH
t
WLWH
t
WHQX
t
QVWH
DATA OUTA0–A7 FROM PCLINSTR IN
INSTRUCTION
ALE
CLOCK
OUTPUT DATA
WRITE TO SBUF
INPUT DATA
CLEAR RI
SU00026
Figure 20. External Data Memory Write Cycle
012345678
t
XLXL
t
t
QVXH
t
XHDV
VALID
XHQX
12304567
t
XHDX
VALIDVALIDVALIDVALIDVALIDVALIDVALID
SET TI
SET RI
SU00027
Figure 21. Shift Register Mode Timing
VCC–0.5
0.45V
0.7V
CC
0.2VCC–0.1
t
CHCL
t
CLCX
t
CLCL
t
CHCX
t
CLCH
SU00009
Figure 22. External Clock Drive
2002 Jan 15
31
Page 32
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
VCC–0.5
0.45V
NOTE:
AC inputs during testing are driven at VCC –0.5 for a logic ‘1’ and 0.45V for a logic ‘0’.
Timing measurements are made at VIH min for a logic ‘1’ and VIL max for a logic ‘0’.
Figure 23. AC Testing Input/Output
0.2V
+0.9
CC
–0.1
0.2V
CC
SU00717
60
55
50
45
40
89C51/89C52/89C54/89C58
V
+0.1V
V
NOTE:
For timing purposes, a port is no longer floating when a 100mV change from
load voltage occurs, and begins to float when a 100mV change from the loaded
V
OH/VOL
LOAD
LOAD
V
–0.1V
LOAD
level occurs. IOH/IOL ≥±20mA.
TIMING
REFERENCE
POINTS
Figure 24. Float Waveform
V
OH
V
OL
SU00718
–0.1V
+0.1V
I
CC
(mA)
35
30
25
20
15
10
5
0
4812162024283236
Frequency at XTAL1 (MHz)
Icc MAX. ACTIVE MODE
Icc MAX ACTIVE MODE (TYP.)
Icc MAX. IDLE MODE
Icc IDLE MODE (TYP.)
SU01495
Figure 25. ICC vs. FREQ
Valid only within frequency specifications of the device under test
2002 Jan 15
32
Page 33
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
V
CC
I
CC
V
CC
SU00719
V
CC
0.7V
0.2VCC–0.1
t
CHCL
V
CC
RST
(NC)
CLOCK SIGNAL
XTAL2
XTAL1
V
SS
Figure 26. ICC Test Condition, Active Mode
All other pins are disconnected
VCC–0.5
Figure 28. Clock Signal Waveform for ICC Tests in Active and Idle Modes
P0
EA
0.45V
CC
t
CLCH
= t
t
CLCX
CHCL
t
CLCL
= 5ns
89C51/89C52/89C54/89C58
RST
(NC)
CLOCK SIGNAL
Figure 27. ICC Test Condition, Idle Mode
All other pins are disconnected
t
CHCX
t
CLCH
SU00009
XTAL2
XTAL1
V
SS
V
CC
P0
EA
V
I
CC
V
SU00720
CC
CC
V
CC
I
CC
V
CC
P0
V
SU00016
CC
(NC)
RST
XTAL2
XTAL1
V
SS
EA
Figure 29. ICC Test Condition, Power Down Mode
All other pins are disconnected. V
= 2V to 5.5V
CC
2002 Jan 15
33
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Philips SemiconductorsProduct data
PROTECTION DESCRIPTION
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Security
The security feature protects against software piracy and prevents the contents of the FLASH from being read. The Security Lock bits are
located in FLASH. The 89C51/89C52/89C54/89C58 has 3 programmable security lock bits that will provide different levels of protection for the
on-chip code and data (see Table 8). Unlike the ROM and OTP versions, the security lock bits are independent. LB3 includes the security
protection of LB1.
Table 8.
SECURITY LOCK BITS
Level
LB1
LB2Program verification is disabled
LB3External execution is disabled.
NOTE:
1. The security lock bits are independent.
1
MOVC instructions executed from external program memory are disabled from fetching code bytes from
internal memory.
89C51/89C52/89C54/89C58
2002 Jan 15
34
Page 35
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
LQFP44:plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mmSOT389-1
89C51/89C52/89C54/89C58
2002 Jan 15
37
Page 38
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
REVISION HISTORY
Release dateCPCNModifications to previous release
2002 Jan 159397 750 09302PROGRAMMING ALGORITHM MODIFIED due to process change (see device comparison table).
PQFP package replaced by LQFP package (dimensions see end of data sheet).
Lower power consumption due to process change.
DEVICE COMPARISON TABLE inserted (beginning of data sheet).
Selection Table for Flash devices updated and extended.
Ordering information table updated.
Erase and program cycles increased from 100 to 10,000.
1999 Oct 279397 750 06613Combined data sheet for all four parts (89C51/52/54/58).
89C51/89C52/89C54/89C58
2002 Jan 15
38
Page 39
Philips SemiconductorsProduct data
80C51 8-bit microcontroller family
4K/8K/16K/32K Flash
Data sheet status
Product
Data sheet status
Objective data
Preliminary data
Product data
[1] Please consult the most recently issued data sheet before initiating or completing a design.
[2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL
http://www.semiconductors.philips.com.
[1]
status
Development
Qualification
Production
[2]
Definitions
Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For
detailed information see the relevant data sheet or data handbook.
Limiting values definition — Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one
or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or
at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended
periods may affect device reliability.
Application information — Applications that are described herein for any of these products are for illustrative purposes only. Philips
Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or
modification.
Disclaimers
Life support — These products are not designed for use in life support appliances, devices or systems where malfunction of these products can
reasonably be expected to result in personal injury . Philips Semiconductors customers using or selling these products for use in such applications
do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application.
Right to make changes — Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard
cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no
responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these
products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless
otherwise specified.
Contact information
For additional information please visit
http://www.semiconductors.philips.com .Fax: +31 40 27 24825
For sales offices addresses send e-mail to:
sales.addresses@www.semiconductors.philips.com.
Definitions
This data sheet contains data from the objective specification for product development.
Philips Semiconductors reserves the right to change the specification in any manner without notice.
This data sheet contains data from the preliminary specification. Supplementary data will be
published at a later date. Philips Semiconductors reserves the right to change the specification
without notice, in order to improve the design and supply the best possible product.
This data sheet contains data from the product specification. Philips Semiconductors reserves the
right to make changes at any time in order to improve the design, manufacturing and supply.
Changes will be communicated according to the Customer Product/Process Change Notification
(CPCN) procedure SNW-SQ-650A.
Document order number:9397 750 09302
89C51/89C52/89C54/89C58
Koninklijke Philips Electronics N.V. 2002
All rights reserved. Printed in U.S.A.
Date of release: 01-02
2002 Jan 15
39
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