DS89C420-ENG Maxim Integrated Products, DS89C420-ENG Datasheet - Page 42

• Manufacturer Part Number: DS89C420-ENG
• Description: IC MCU ULTRA 25MHZ HP 44-TQFP
• Manufacturer: Maxim Integrated Products
• Series: 89Cr

Specifications of DS89C420-ENG

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: EBI/EMI, SIO, UART/USART
• Peripherals: Power-Fail Reset, WDT
• Number Of I /o: 32
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

DS89C420 Ultra-High-Speed Microcontroller
An external reset by the RST pin unconditionally exits the processor from stop mode. If the BGS bit is set to logic 1,
the bandgap provides a reset while in stop mode if V
should drop below the V
level. If BGS is 0, no reset is
CC
RST
generated if V
drops below V
.
CC
RST
When the stop mode is removed, the processor waits for 65,536 clock cycles for the internal flash memory to warm
up before starting normal execution. Also, the processor waits for the crystal warmup period if not using the ring
oscillator.
SERIAL I/O
The DS89C420 provides a serial port (UART) that is identical to the 80C52. In addition, it includes a second
hardware serial port that is a full duplicate of the standard one. This port optionally uses pins P1.2 (RXD1) and
P1.3 (TXD1) and has duplicate control functions included in new SFR locations.
Both ports can operate simultaneously but can be at different baud rates or even in different modes. The second
serial port has similar control registers (SCON1 at C0h, SBUF1 at C1h) as the original. The new serial port can
only use timer 1 for timer-generated baud rates.
Control for serial port 0 is provided by the SCON0 register while its I/O buffer is SBUF0. Registers SCON1 and
SBUF1 provide the same functions for the second serial port. A full description of the use and operation of both
serial ports is in the Ultra-High-Speed Flash Microcontroller User’s Guide.
INSTRUCTION SET
The DS89C420 instructions are 100% binary compatible with the industry standard 8051, and are only different in
the number of machine cycles used for the instructions. Some special conditions and features should be
considered when analyzing the DS89C420 instruction set. Full details are given in the Ultra-High-Speed Flash
Microcontroller User’s Guide.
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