ATA8741 ATMEL Corporation, ATA8741 Datasheet - Page 176

• Manufacturer Part Number: ATA8741
• Manufacturer: ATMEL Corporation

27.0.3
27.1
176
Addressing the Flash During Self-Programming
ATA8741
Performing a Page Write
To execute Page Write, set up the address in the Z-pointer, write “00000101” to SPMCSR and
execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored.
The page address must be written to PCPAGE. Other bits in the Z-pointer must be written to
zero during this operation.
• The CPU is halted during the Page Write operation.
The Z-pointer is used to address the SPM commands.
Since the Flash is organized in pages (see
be treated as having two different sections. One section, consisting of the least significant bits, is
addressing the words within a page, while the most significant bits are addressing the pages.
This is shown in
are addressed independently. Therefore it is of major importance that the software addresses
the same page in both the Page Erase and Page Write operation.
The LPM instruction uses the Z-pointer to store the address. Since this instruction addresses the
Flash byte-by-byte, also the LSB (bit Z0) of the Z-pointer is used.
Figure 27-1. Addressing the Flash During SPM
Note:
Bit
ZH (R31)
ZL (R30)
Z - REGISTER
1. The different variables used in
PROGRAM MEMORY
BIT
PAGE
PROGRAM
COUNTER
15
Figure 28-1 on page
Z15
Z7
15
7
PAGE ADDRESS
WITHIN THE FLASH
ZPCMSB
PCMSB
Z14
14
Z6
6
PCPAGE
Z13
Z5
13
5
184. Note that the Page Erase and Page Write operations
Figure 27-1
ZPAGEMSB
PAGEMSB
Table 28-7 on page
PCWORD
Z12
12
Z4
4
WORD ADDRESS
WITHIN A PAGE
(1)
are listed in
1
Z11
0
0
Z3
11
3
INSTRUCTION WORD
PAGE
Table 28-7 on page
Z10
10
Z2
2
183), the Program Counter can
Z9
Z1
9
1
PCWORD[PAGEMSB:0]:
00
01
02
PAGEEND
183.
9140B–INDCO–07/09
Z8
Z0
8
0