AN2400 Freescale Semiconductor / Motorola, AN2400 Datasheet - Page 14

• Manufacturer Part Number: AN2400
• Description: HCS12 NVM Guidelines
• Manufacturer: Freescale Semiconductor / Motorola

Freescale Semiconductor, Inc.
AN2400/D
The standard Flash block sizes are 32k bytes, 64k bytes and 128k bytes. A
microcontroller may have a single Flash block of 32k, 64k or 128k bytes, or may
have multiple blocks, up to a total of 512k bytes. Each Flash block can be
programmed independently and simultaneously, thus enabling microcontroller
programming times to be minimised.
The Flash memory is programmed in units of aligned words, i.e. two bytes at a
time. The data word is written to an even address, i.e. bit 0 of the address is
clear. This will result in the bytes at the even address and the even address
plus one being programmed.
The Flash erase sector size is 512 bytes for 32k and 64k byte Flash blocks. To
erase an entire sector, any data value is written to any Flash address within the
required sector. That is to say, only address bits [15:9] are required to
determine the erase sector. For a 128k byte Flash block, the erase sector size
is 1024 bytes and address bits [15:10] determine the required sector.
The command register, address register and data registers are buffered to
allow pipelined programming. Pipelined programming allows the next address,
data and command to be loaded while the current command is still executing,
thus reducing the overall programming time.
Flash has a mode called Burst programming. Burst programming is invoked by
pipelining program commands for words on the same Flash row. A row is 64
bytes on 32k and 64k byte Flash blocks and 128 bytes on the 128k Flash block.
Burst programming reduces the programming time by keeping the high voltage
generation switched on between program commands on the same row. Burst
programming isapproximately twice as fast as single word programming.
Flash may also be used to emulate EEPROM on microcontrollers that do not
have EEPROM, refer to application note AN2302/D for details and example
software.
The Flash control registers are located at the register base address + $100 to
$10F. The register base address is set by the INITRG register, the base
address after a reset is $0000.
14
HCS12 NVM Guidelines
MOTOROLA
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