IAP example with SPI

AN2737

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support the status register management. Consequently, it is not possible to read or write the

status register.

2.3

Read and write commands

The current example has been validated at 4 MHz for read and write operations. The

firmware allows reading or writing in the Flash program memory and data EEPROM of the

STM8 from address 8000h—027FFFh and 4000h—47FFh respectively.

Before starting, the firmware example must be loaded with STVD in the STM8 device and

executed using the run command. The evaluation board LCD displays a welcome message

‘STM8 IAP-SPI Demo’. No more messages are displayed during firmware execution.

2.3.1

Packet description

The different packets composing an SPI command are:

1.

2.

OPC-WREN: Opcode (06h) that enables the write function.

3.

4.

ADD: Physical address of the memory which is used to start a read or write operation.

5.

DATA-R: Number of data to be read. It is used only for clocking (commonly these bytes

have a value of 00h).

6.

DATA-W: Data to be programmed into the Flash program memory or data EEPROM.

2.3.2

Read command

The read command allows data from the Flash program memory of the STM8 to be read,

starting from any Flash addressing range.

The packet sequence to achieve a ‘read’ with the Aardvark software and the STM8 SPI is

summarized in Figure 10. During this sequence, the NSS signal is set to GND by the

master.

Figure 10.

Read packet sequence

OPC-READ

ADD

DATA-R

00h

Flash program memory data read

MOSI line

MISO line

00h