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) with a boot loader), see the 89C51RC+/89C51RD+ datasheet.49104

Both 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.

FEATURES

• 80C51 Central Processing Unit

• On-chip FLASH Program Memory

• Speed up to 33 MHz

• Full static operation

• RAM expandable externally to 64 k bytes

• 4 level priority interrupt

• 6 interrupt sources

• Four 8-bit I/O ports

• Full-duplex enhanced UART

– Framing error detection

– Automatic address recognition

• Power control modes

– Clock can be stopped and resumed

– Idle mode

– Power down mode

• Programmable clock out

• Second DPTR register

• Asynchronous port reset

• Low EMI (inhibit ALE)

• 3 16-bit timers

•Wake up from power down by an external interrupt

FLASH EPROM MEMORY

General Description

The 89C51/89C52/89C54/89C58 FLASH reliably stores memory contents even after 100 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 = 0)

• Programmable security bits

• 100 minimum erase/program cycles for each byte

• 10 year minimum data retention

• Programming support available from many popular vendors

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.

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 pide-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 VCC and RST must come up at the same time for a proper start-up. Ports 1, 2, and 3 will asynchronously be driven to their reset condition when a voltage above VIH1 (min.) is applied to RESET. The value on the EA pin is latched when RST is deasserted and has no further effect.

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.