Datasheet

Functional overview STM8L050J3
18/94 DS12167 Rev 4
3.5 Low power real-time clock
The real-time clock (RTC) is an independent binary coded decimal (BCD) timer/counter.
Six byte locations contain the second, minute, hour (12/24 hour), week day, date, month,
year, in BCD (binary coded decimal) format. Correction for 28, 29 (leap year), 30, and 31
day months are made automatically.
It provides a programmable alarm and programmable periodic interrupts with wakeup from
Halt capability.
• Periodic wakeup time using the 32.768 kHz LSE with the lowest resolution (of 61 µs) is
from min. 122 µs to max. 3.9 s. With a different resolution, the wakeup time can reach
36 hours
• Periodic alarms based on the calendar can also be generated from every second to
every year
3.6 Memories
STM8L050J3 as all the low density value line STM8L05xxx devices have the following main
features:
• Up to 1 Kbyte of RAM
• The non-volatile memory is divided into three arrays:
– 8 Kbytes of low-density embedded Flash program memory
– 256 bytes of Data EEPROM
– Option bytes
The EEPROM embeds the error correction code (ECC) feature.
The option byte protects part of the Flash program memory from write and readout piracy.
Recommendation for the device's programming
The device's 8 Kbytes program memory is not empty on virgin devices; there is code loop
implemented on the reset vector. It is recommended to keep valid code loop in the device to
avoid the program execution from an invalid memory address (which would be any memory
address out of 8 Kbytes program memory space).
If the device's program memory is empty (0x00 content), it displays the behavior described
below:
• After the power on, the “empty” code is executed (0x0000 opcodes = instructions: NEG
(0x00, SP)) until the device reaches the end of the 8 Kbytes program memory (the end
address = 0x9FFF).
It takes around 4 milliseconds to reach the end of the 8 Kbytes memory space @2 MHz
HSI clock.
• Once the device reaches the end of the 8 Kbytes program memory, the program
continues and code from a non-existing memory is fetched and executed.
The reading of non-existing memory is a random content which can lead to the execution of
invalid instructions.
The execution of invalid instructions generates a software reset and the program starts
again. A reset can be generated every 4 milliseconds or more.
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