257
AT90PWM216/316 [DATASHEET]
7710H–AVR–07/2013
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: Self Programming 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.
23.6
Addressing the Flash During Self-Programming
The Z-pointer is used to address the SPM commands.
ing 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 is1 shown in
Figure 23-3. Note that the Page
Erase and Page Write operations are addressed independently. Therefore it is of major importance that the Boot
Loader software addresses the same page in both the Page Erase and Page Write operation. Once a program-
ming operation is initiated, the address is latched and the Z-pointer can be used for other operations.
The only SPM operation that does not use the Z-pointer is Setting the Boot Loader Lock bits. The content of the Z-
pointer is ignored and will have no effect on the operation. The LPM instruction does also use 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.
Bit
151413
1211
10
9
8
ZH (R31)
Z15
Z14
Z13
Z12
Z11
Z10
Z9
Z8
ZL (R30)
Z7Z6
Z5Z4
Z3Z2
Z1Z0
76
54
32
10