mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 58

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

Memory
4.4
The flash memory is intended primarily for program storage and read-only data. In-circuit programming
allows the operating program to be loaded into the flash memory after final assembly of the application
product. It is possible to program the entire array through the single-wire background debug interface.
Because no special voltages are needed for flash erase and programming operations, in-application
programming is also possible through other software-controlled communication paths.
Flash memory is ideal for single-supply applications allowing for field reprogramming without requiring
external high voltage sources for program or erase operations. The flash module includes a memory
controller that executes commands to modify flash memory contents.
Array read access time is one bus cycle for bytes, aligned words, and aligned longwords. Multiple accesses
are needed for misaligned word and longword operands. For flash memory, an erased bit reads 1 and a
programmed bit reads 0. It is not possible to read from a flash block while any command is executing on
that specific flash block.
Flash memory on MCF51AC256 series MCUs must be programmed 32 bits at a time. The MCF51AC256
series flash memory is organized as two 16-bit wide blocks interleaved to yield a 32-bit data path.
4.4.1
Features of the flash memory include:
4.4.2
The flash module contains a set of 16 control and status registers. Flash registers are byte accessible only.
Detailed descriptions of each register bit are provided in the following sections.
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Flash size
— MCF51AC256: 262,144 bytes (128 sectors of 2048 bytes each)
— MCF51AC128: 131,072 bytes (64 sectors of 2048 bytes each)
Automated program and erase algorithm
Fast program and sector erase operation
Burst program command for faster flash array program times
Single power supply program and erase
Command interface for fast program and erase operation
Up to 100,000 program/erase cycles at typical voltage and temperature
Flexible block protection (on any 2 KB memory boundary)
Security feature to prevent unauthorized access to on-chip memory and resources
Auto power-down for low-frequency read accesses
Flash Memory
Features
Register Descriptions
A flash block address must be in the erased state before being programmed.
Cumulative programming of bits within a flash block address is not allowed
except for status field updates required in EEPROM emulation applications.
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
CAUTION
Freescale Semiconductor