DS89C420-MNL Maxim Integrated Products, DS89C420-MNL Datasheet - Page 22

• Manufacturer Part Number: DS89C420-MNL
• Description: IC MCU ULTRA 33MHZ HP 40-DIP
• Manufacturer: Maxim Integrated Products
• Series: 89Cr

Specifications of DS89C420-MNL

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 33MHz
• 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: 40-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

Table 3. Flash Memory Lock Bits
The DS89C420 provides user-selectable options that must be set before beginning software execution. The option
control register uses flash bits rather than SFRs, and is individually erasable and programmable as a byte-wide
register. Bit 3 of this register is defined as the watchdog POR default. Setting this bit to 1 disables the watchdog-
reset function on power-up, and clearing this bit to 0 enables the watchdog-reset function automatically. Other bits
of this register are undefined and are at logic 1 when read. The value of this register can be read at address FCh in
parallel programming mode or when executing a verify-option control-register instruction in ROM loader mode.
The signature bytes can be read in ROM loader mode or in parallel programming mode. Reading data from
addresses 30h, 31h, and 60h provides signature information about manufacturer, part, and extension as follows:
ROM LOADER
The full 16kB of on-chip flash program-memory space, security flash block, and external SRAM can be
programmed in-system from an external source through serial port 0 under the control of a built-in ROM loader.
The ROM loader also has an auto-baud feature that determines which baud rate frequencies are being used for
communication and sets up the baud rate generator for communication at that frequency.
When the DS89C420 is powered up and has entered its user operating mode, the ROM loader mode can be
invoked at any time by forcing RST = 1, EA = 0, and PSEN = 0. It remains in effect until power-down or when the
condition (RST = 1 and PSEN = EA = 0) is removed. Entering the ROM loader mode forces the processor to start
fetching from the 2kB internal ROM for program memory initialization and other loader functions.
The read/write accessibility is determined by the state of the lock bits, which can be verified directly by the ROM
loader. In the ROM loader mode, a mass-erase operation also erases the memory bank select and sets it to the
default state. Otherwise, the memory bank select cannot be altered in the ROM loader mode.
Flash programming is executed by a series of internal flash commands that are derived (by the built-in ROM
loader) from data transmitted over the serial interface from a host PC. PC-based software tools that configure and
load the microcontrollers are available at www.maxim-ic.com/micros/ftpinfo.html.
Full details of the ROM loader software and its implementation are given in the Ultra-High-Speed Flash
Microcontroller User’s Guide.
LEVEL
1
2
3
4
LB1
X
X
1
0
LB2
X
1
1
0
ADDRESS VALUE
30h DAh
31h 42h
60h 01h
LB3
1
1
1
0
No program lock. Encrypted verify if encryption array is programmed.
Prevent MOVC in external memory from reading program code in internal
memory. EA is sampled and latched on reset. Allow no further parallel or
program memory loader programming.
Level 2 plus no verify operation. Also prevent MOVX in external memory
from reading internal SRAM.
Level 3 plus no external execution.
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DS89C420 Device ID
Device Extension
Manufacturer ID
FUNCTION
PROTECTION