DS89C430 datasheet(22/46 Pages) DALLAS

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DS89C430/DS89C450 Ultra-High-Speed Flash Microcontrollers

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fetch that takes four clocks. Page mode 1 is the only external addressing mode where the CPU does not require

stalls for external memory access, but page misses result in reduced external access performance.

On-Chip Program Memory

The processor can fetch the entire on-chip program memory range automatically. By default, the reset routines and

all interrupt vectors are located in the lower 128 bytes of the on-chip program memory.

On-chip program memory is logically divided into pairs of 8kB, 16kB, or 32kB flash memory banks to support in-

application programming. The upper block of the on-chip program memory is designed to be programmed in-

application with the standard 5V VCC supply under the control of the user software or by using a built-in program

memory loader. It can also be programmed in standard flash or EPROM programmers. The DS89C430

incorporates a memory management unit (MMU) and other hardware to support any of the three programming

methods. The MMU controls program and data memory access, and provides sequencing and timing controls for

programming of the on-chip program memory. A separate security flash block supports a three-level lock, a 64-byte

encryption array, and other flash options.

Security Features

The DS89C430 incorporates a 64-byte encryption array, allowing the user to verify program codes while viewing

the data in encrypted form. The encryption array is implemented in a security flash memory block that has the

same electrical and timing characteristics as the on-chip program memory. Once the encryption array is

programmed to non-FFh, the data presented in the verify mode is encrypted. Each byte of data is XNORed with a

byte in the encryption array during verification.

A three-level lock restricts viewing of the internal program and data memory contents. By programming the three

lock bits, the user can select a level of security as specified in Table 3. The protection levels function differently

than those in a traditional 8051 microcontroller, and should not be used while executing external code.

Once a security level is selected and programmed, the setting of the lock bits remains. Only a mass erase can

erase these bits and allow reprogramming the security level to a less restricted protection.

Table 3. Flash Memory Lock Bits

LEVEL

LB1

LB2

LB3

PROTECTION

No program lock. Encrypted verify if encryption array is programmed. Do

not execute external program code while operating at this security level.

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. Do not execute external program

code while operating at this security level.

Level 2 plus no verify operation. Also prevent MOVX in external memory

from reading internal SRAM. Do not execute external program code while

operating at this security level.

Level 3 plus no external execution.

The DS89C430 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

function on power-up. Clearing this bit to 0 enables the watchdog reset function automatically. Other bits of this

parallel programming mode or executing a verify-option-control register instruction in ROM loader mode or in-

application programming mode.

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