User's Manual

UMXXX
• The SRAM is divided in two banks
o 12KB from 0x2000_0000 to 0x2000_2FFF, retention always-on
o 12KB from 0x2000_3000 to 0x2000_5FFF, retention optional
o The FULL BLE stack needs 9.6KB of SRAM; see below for FULL BLE stack
features.
o The BASIC BLE stack needs 0.0KB of SRAM; see below for BASIC BLE
stack features.
• The Flash is 256KB from 0x1004_0000 to 0x1007_FFFF
o The FULL BLE stack needs 77KB, leaving 179KB for the user application;
the FULL BLE stack will support concurrent peripheral and central roles
(N=0,1,2 connections to other centrals and 8-N connections to other
peripherals), LE secure connections, controller privacy, extended data
length.
o The BASIC BLE stack needs 58KB, leaving 198KB for the user
application; the BASIC BLE stack will support only the peripheral role (1
connection to a central), only legacy security, no controller privacy and no
extended data length.
o The OTA manager to enable over-the-air firmware updates adds 10KB to
the size of the BLE stack. The OTA manager may be independent of the
user application, or it may be embedded in the user application.
When the OTA manager is independent of the user application, the Flash is divided in two
section. The first relatively small section is dedicated to the OTA application; the size is the
sum of BLE stack size and OTA manager size. The second large section is dedicated to
the user application and is made of the rest of the Flash. This has the advantage of leaving
the largest space to the user application, but it has the disadvantage that there is no
application to run if the update is not completed successfully.
When the OTA manager is embedded in the user application, the Flash is divided in three
sections. The first section is dedicated to the current old application; the size is the sum of
BLE stack size, OTA manager size and user application size. The second section is
dedicated to the new updated application; the size is the same as the first section. The third
very small section is dedicated to the reset application; the reset application decides which
application to run after boot, depending on what is available and valid in the first two
sections. This has the advantage that even if the update is not completed successfully,
there will always be a valid old application to run. The disadvantage is that the space
available for the user application is less than half the size of the Flash. Note that after a