參數(shù)資料
型號(hào)： P87CL52X2
廠商： NXP Semiconductors N.V.
英文描述： 80C51 8-bit microcontroller family
中文描述： 80C51的8位單片機(jī)系列
文件頁(yè)數(shù)： 8/47頁(yè)
文件大?。?/td> 301K
代理商： P87CL52X2
Philips Semiconductors
Product data
P87CL52X2/54X2
80C51 8-bit microcontroller family
8K/16K OTP 256 bytes RAM ROMless low voltage
(1.8 V to 3.3 V), low power, high speed (33 MHz)
2003 May 14
8
OSCILLATOR 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, as shown in the logic symbol.
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.
Clock Control Register (CKCON)
This device provides control of the 6-clock/12-clock mode by an
SFR bit (bit X2 in register CKCON). When X2 is 0, 12-clock mode is
activated. By setting this bit to 1, the system is switching to 6-clock
mode. Having this option implemented as SFR bit, it can be
accessed anytime and changed to either value. Changing X2 from 0
to 1 will result in executing user code at twice the speed, since all
system time intervals will be divided by 2. Changing back from
6-clock to 12-clock mode will slow down running code by a factor of
2.
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-up 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.
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 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
CC
to
the minimum specified operating voltages before the Power Down
Mode is terminated.
For the P87CL5xX2, 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. WUPD
(AUXR1.3–Wakeup from Power Down) enables or disables the
wakeup from power down with external interrupt. Where:
WUPD = 0 Disable
WUPD = 1 Enable
To properly terminate Power Down the reset or external interrupt
should not be executed before V
CC
is restored to its normal
operating level and must be held active long enough for the
oscillator to restart and stabilize (normally less than 10 ms).
With an external interrupt, INT0 or 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.
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
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 is high;
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 are weakly pulled
high. The oscillator circuit remains active. While the P87CL5xX2 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.
Table 2. External Pin Status During Idle and Power-Down Modes
MODE
PROGRAM MEMORY
ALE
PSEN
PORT 0
PORT 1
PORT 2
PORT 3
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
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