P89C51X2 View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
P89C51X2 Datasheet PDF : 48 Pages
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Philips Semiconductors
80C51 8-bit Flash microcontroller family
4K/8K/16K/32K Flash
Preliminary data
P89C51X2/52X2/54X2/58X2
FLASH EPROM MEMORY
General Description
The P89C51X2/P89C52X2/P89C54X2/P89C58X2 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 kbyte external program memory if the internal program
memory is disabled (EA = 0)
• Programmable security bits
• 10,000 minimum erase/program cycles for each byte
• 10 year minimum data retention
• Programming support available from many popular vendors
OSCILLATOR CHARACTERISTICS
Using the oscillator, 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. 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 both
an SFR bit (bit X2 in register CKCON) and a Flash bit (bit FX2,
located in the Security Block). 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.
The Flash clock control bit (FX2) activates the 6-clock mode when
programmed using a parallel programmer, superceding the X2 bit
(CKCON.0). Please also see Table 2 below.
Table 2.
FX2 clock mode bit
(can only be set by
parallel programmer)
erased
X2 bit
(CKCON.0)
0
erased
1
programmed
X
CPU clock mode
12-clock mode
(default)
6-clock mode
6-clock mode
Programmable Clock-Out Pin
A 50% duty cycle clock can be programmed to be output 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 61 Hz to 4 MHz at
a 16 MHz operating frequency in 12-clock mode (122 Hz to
8 MHz in 6-clock mode).
To configure the Timer/Counter 2 as a clock generator, bit C/T2 (in
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
n (65536–RCAP2H, RCAP2L)
Where:
n = 2 in 6-clock mode, 4 in 12-clock mode.
(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.
RESET
A reset is accomplished by holding the RST pin HIGH for at least
two machine cycles (24 oscillator periods in 12-clock and 12
oscillator periods in 6-clock mode), while the oscillator is running. To
insure a reliable 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, unless it has been set to
6-clock operation using a parallel programmer.
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 idle mode (see Table 3), 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.
2002 Jun 06
11
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