AN1827 Freescale Semiconductor / Motorola, AN1827 Datasheet - Page 14

• Manufacturer Part Number: AN1827
• Description: Programming and Erasing FLASH Memory on the MC68HC908AS60
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
14
Although the overall procedure is relatively simple, step 3 could use
some clarification. Since the specified address is any address within the
block to erase, the microcontroller must somehow know exactly which
memory range to erase. This is where the "cared address" becomes
important.
In step 2, the size of the block to erase is set by writing to the BLK bits
in the FLCR.
in one erase operation.
When an address is specified in step 3, certain address lines are latched
pertaining to this block size, and they establish the start and end
addresses of the block. The larger the erase block, the smaller the size
of the cared address.
For example, if the BLK bits are set such that the erase block size is a
single row (BLK0 = BLK1 = 1), and the address $9AF0 is specified in
step 3, then bits 15–6 of $9AF0 are the "cared addresses." Therefore,
the values of these address bits are fixed.
Bit No.
BLK1
Binary
Freescale Semiconductor, Inc.
Hex
0
0
1
1
For More Information On This Product,
15
BLK0
1
Go to: www.freescale.com
Table 2
0
1
0
1
Figure 4. Cared Address Example $9AF0
14
0
9
13
shows the various block sizes which can be erased
0
Table 2. Erase Block Sizes
Cared Addresses
One-half array: 16 Kbytes
Eight rows: 512 bytes
Full array: 32 Kbytes
Single row: 64 bytes
12
1
Block Size
11
1
10
0
A
9
1
8
0
7
1
6
1
F
Cared Addresses
5
1
A15–A14
4
1
A15–A9
A15–A6
A15
3
0
MOTOROLA
2
0
0
AN1827
1
0
0
0