DocID018532 Rev 3

9/13

PM0083

Software interface

2.5

Read the status of the option bytes

2.5.1

Programming mode entry

Follow the steps described in Section 2.4: Programming mode entry on page 7.

2.5.2

Option read

Option read checks the option status by writing a data byte to a specific RAM address of the

STM8T143, and then reading the option status returned by the STM8T143. Data is written

to the STM8T143 by giving it a command first, then sending it the address and finally

sending it the data.

Table 7. Option read procedure

Step

Action

Description

1.

Write 0x40 to STM8T143 0x40 is the command to be given before writing data.

2.

Write 0x0A to

STM8T143

0x0A is the address to write data to for option status enquiry.

3.

Write 0x1i to STM8T143

(i = 0, 1 or 2)

Send the option byte number (i) ORed with instruction 0x10.

4.

Write 0x40 to STM8T143 0x40 is the command to be given before writing data.

5.

Write 0x0A to

STM8T143

0x0A is the address to write data to for option status enquiry.

6.

Write 0x0i (i = 0, 1 or 2)

Send the option byte number to the STM8T143.

7.

Write 0x30 to STM8T143

0x30 is the command to be given before reading data from a RAM

address of the STM8T143.

8.

Write 0x0B to

STM8T143

0x0B is the option data address.

9.

Read from STM8T143

Shift "dummy" data (0x00) out to STM8T143, simultaneously

shifting data in from STM8T143.

10.

Repeat steps 1 to 9 for

option bytes 1 and 2.

Each option byte's status (for 8 option bits) is read in the same

manner.

Note: Option bytes are read in the following order: byte0, byte1

and byte2.

11. STM8T143 power OFF

VDD = 0 V