MC68HC908AZ60 Datasheet, PDF (40/480 Pages) Motorola, Inc – HCMOS Microcontroller Unit

FLASH-1 Memory
change, as will the block protection. The new silicon can be identified by
an ‘A’ suffix, i.e. 68HC908AZ60A, and by mask set.
NOTE:
In order that current software is compatible and also to prevent problems
if code should runaway, Flash program and erase algorithms should not
be embedded in software.
Functional Description
The FLASH memory physically consists of two independent arrays of 32K
bytes with an additional 52 bytes of user vectors and two bytes of block
protection. An erased bit reads as a logic 0 and a programmed bit reads
as a logic 1. Program and erase operations are facilitated through control
bits in a memory mapped register. Details for these operations appear
later in this section. Memory in the FLASH array is organized into pages
within rows. There are 8 pages of memory per row with 8 bytes per page.
The minimum erase block size is a single row, 64 bytes. Programming is
performed on a per page basis; eight bytes at a time. The address ranges
for the user memory, control register and vectors are:
• $8000–$FDFF
• $FF80–FF81 (Block Protect Registers)
• $FE0B FLASH Control Register
• $FFCC–$FFFF (These locations are reserved for user-defined
interrupt and reset vectors.)
When programming the FLASH, just enough program time must be used
to program a page. Too much program time can result in a program
disturb condition; in which case an erased bit on the row being
programmed becomes unintentionally programmed. Program disturb is
avoided by using an iterative program and margin read technique known
as the smart programming algorithm. The smart programming algorithm
is required whenever programming the FLASH (See FLASH
Program/Margin Read Operation on page 43). As well, to avoid the
program disturb issue, each storage page of the row should not be
programmed more than once before it is erased. The 8 program cycle
maximum per row aligns with the architecture’s 8 pages of storage per
MC68HC908AZ60 — Rev 2.0
38
FLASH-1 Memory
4-flash-1
MOTOROLA