STR910FAM32 datasheet(16/101 Pages) STMICROELECTRONICS

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Functional overview

STR91xFAx3x, STR91xFAx4x

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Both Flash memories are blank when devices are shipped from ST. The CPU can boot only

from Flash memory (configurable selection of which Flash bank).

Flash memories are programmed half-word (16 bits) at a time, but are erased by sector or

by full array.

3.7.1

Primary Flash memory

Using the STR91xFA device configuration software tool and 3rd party Integrated Developer

Environments, it is possible to specify that the primary Flash memory is the default memory

from which the CPU boots at reset, or otherwise specify that the secondary Flash memory is

the default boot memory. This choice of boot memory is non-volatile and stored in a location

that can be programmed and changed only by JTAG In-System Programming. See

Section 6: Memory mapping, for more detail.

The primary Flash memory has equal length 64K byte sectors. See Table 3 for number of

sectors per device type.

3.7.2

Secondary Flash memory

The smaller of the two Flash memories can be used to implement a bootloader, capable of

storing code to perform robust In-Application Programming (IAP) of the primary Flash

memory. The CPU executes code from the secondary Flash, while updating code in the

primary Flash memory. New code for the primary Flash memory can be downloaded over

any of the interfaces on the STR91xFA (USB, Ethernet, CAN, UART, etc.)

Additionally, the Secondary Flash memory may also be used to store small data sets by

emulating EEPROM through firmware, eliminating the need for external EEPROM

memories. This raises the data security level because passcodes and other sensitive

information can be securely locked inside the STR91xFA device.

The secondary Flash memory is sectored as shown in Table 4 according to device type.

Both the primary Flash memory and the secondary Flash memory can be programmed with

code and/or data using the JTAG In-System Programming (ISP) channel, totally

independent of the CPU. This is excellent for iterative code development and for

manufacturing.

Table 3.

Sectoring of primary Flash memory

Size of Primary Flash

256 KBytes

512 KBytes

1 MByte

2 MBytes

Number of sectors

Size of each sector

64 Kbytes

Table 4.

Sectoring of secondary Flash memory

Size of Secondary Flash

32 KBytes

128 KBytes

Number of sectors

Size of each sector

8 Kbytes

16 Kbytes

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