Datasheet

247
ATmega32A [DATASHEET]
Atmel-8155D-AVR-ATmega32A-Datasheet_02/2014
When programming (Page Erase or Page Write) to the RWW section, the RWW section is blocked for reading (the
RWWSB will be set by hardware). To re-enable the RWW section, the user software must wait until the program-
ming is completed (SPMEN will be cleared). Then, if the RWWSRE bit is written to one at the same time as
SPMEN, the next SPM instruction within four clock cycles re-enables the RWW section. The RWW section cannot
be re-enabled while the Flash is busy with a page erase or a page write (SPMEN is set). If the RWWSRE bit is writ-
ten while the Flash is being loaded, the Flash load operation will abort and the data loaded will be lost.
• Bit 3 – BLBSET: Boot Lock Bit Set
If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles sets Boot
Lock bits, according to the data in R0. The data in R1 and the address in the Z-pointer are ignored. The BLBSET
bit will automatically be cleared upon completion of the Lock bit set, or if no SPM instruction is executed within four
clock cycles.
An LPM instruction within three cycles after BLBSET and SPMEN are set in the SPMCR Register, will read either
the Lock bits or the Fuse bits (depending on Z0 in the Z-pointer) into the destination register. See “Reading the
Fuse and Lock Bits from Software” on page 260 for details.
• Bit 2 – PGWRT: Page Write
If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes
Page Write, with the data stored in the temporary buffer. The page address is taken from the high part of the Z-
pointer. The data in R1 and R0 are ignored. The PGWRT bit will auto-clear upon completion of a page write, or if
no SPM instruction is executed within four clock cycles. The CPU is halted during the entire page write operation if
the NRWW section is addressed.
• Bit 1 – PGERS: Page Erase
If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes
Page Erase. The page address is taken from the high part of the Z-pointer. The data in R1 and R0 are ignored. The
PGERS bit will auto-clear upon completion of a page erase, or if no SPM instruction is executed within four clock
cycles. The CPU is halted during the entire page write operation if the NRWW section is addressed.
• Bit 0 – SPMEN: Store Program Memory Enable
This bit enables the SPM instruction for the next four clock cycles. If written to one together with either RWWSRE,
BLBSET, PGWRT’ or PGERS, the following SPM instruction will have a special meaning, see description above. If
only SPMEN is written, the following SPM instruction will store the value in R1:R0 in the temporary page buffer
addressed by the Z-pointer. The LSB of the Z-pointer is ignored. The SPMEN bit will auto-clear upon completion of
an SPM instruction, or if no SPM instruction is executed within four clock cycles. During page erase and page
write, the SPMEN bit remains high until the operation is completed.
Writing any other combination than “10001”, “01001”, “00101”, “00011” or “00001” in the lower five bits will have no
effect.