Datasheet

215
ATtiny828 [DATASHEET]
8371A–AVR–08/12
In addition to the application and boot loader areas, the Flash is also divided into two fixed sections; the Read-While-
Write (RWW) and the No Read-While-Write (NRWW) section. The main difference between the RWW and NRWW
sections are:
z When erasing or writing a page located inside the RWW section, the NRWW section can be read during the
operation
z When erasing or writing a page located inside the NRWW section, the CPU is halted during the entire operation
Note that during a boot loader operation, software can never read code located in the RWW section. See Table 79,
below.
Table 79. Read-While-Write Features
The term “read-while-write section” refers to the section being programmed (i.e. erased, or written), not the section that is
being read during a software update by the boot loader.
Figure 90. Read-While-Write vs. No Read-While-Write
RWW and NRWW sections are defined in Table 82 on page 217 and illustrated in Figure 90.
Section that Z-pointer addresses
during programming
Section that can be read during
programming?
CPU halted
Read-while-write
supported
RWW NRWW No Yes
NRWW None Yes No
Read-While-Write
(RWW) Section
No Read-While-Write
(NRWW) Section
Z-pointer
Addresses RWW
Section
Z-pointer
Addresses NRWW
Section
CPU is Halted
During the Operation
Code Located in
NRWW Section
Can be Read During
the Operation