ST7LITE49M STMicroelectronics, ST7LITE49M Datasheet - Page 34

• Manufacturer Part Number: ST7LITE49M
• Description: 8-bit MCU
• Manufacturer: STMicroelectronics

Specifications of ST7LITE49M

• 4 Kbytes Single Voltage Extended Flash (xflash) Program Memory With Read-out Protection In-circuit Programming And In-application Programming (icp And Iap) Endurance: 10k write/erase cycles guaranteed Data retention
• 128 Bytes Data Eeprom With Read-out Protection. 300k Write/erase Cycles Guaranteed, Data Retention: 20 years at 55 °C.
• Clock Sources: Internal trimmable 8 MHz RC oscillator, auto-wakeup internal low power - low frequency oscillator, crystal/ceramic resonator or external clock
• Five Power Saving Modes: Halt, Active-halt, Auto-wakeup from Halt, Wait and Slow
• A/d Converter: 10 input channels

Supply, reset and clock management
Caution:
7.1.2
Note:
34/188
1
2
3
In 38-pulse ICC mode, the internal RC oscillator is forced as a clock source, regardless of
the selection in the option byte.
Section 13: Electrical characteristics on page 139
and accuracy of the RC oscillator.
To improve clock stability and frequency accuracy, it is recommended to place a decoupling
capacitor, typically 100 nF, between the V
V
These bytes are systematically programmed by ST, including on FASTROM devices.
If the voltage or temperature conditions change in the application, the frequency may need
to be recalibrated. Refer to application note AN1324 for information on how to calibrate the
RC frequency using an external reference signal.
Auto-wakeup RC oscillator
The ST7LITE49M also contains an Auto-wakeup RC oscillator. This RC oscillator should be
enabled to enter auto-wakeup from halt mode.
The auto-wakeup (AWU) RC oscillator can also be configured as the startup clock through
the CKSEL[1:0] option bits (see
This is recommended for applications where very low power consumption is required.
Switching from one startup clock to another can be done in run mode as follows (see
Figure
Case 1 Switching from internal RC to AWU
1.
2.
3.
4.
5.
Case 2 Switching from AWU RC to internal RC
1.
2.
3.
4.
5.
When the internal RC is not selected, it is stopped so as to save power consumption.
When the internal RC is selected, the AWU RC is turned on by hardware when entering
Auto-wakeup from Halt mode.
When the external clock is selected, the AWU RC oscillator is always on.
SSA
Set the RC/AWU bit in the CKCNTCSR register to enable the AWU RC oscillator
The RC_FLAG is cleared and the clock output is at 1.
Wait 3 AWU RC cycles till the AWU_FLAG is set
The switch to the AWU clock is made at the positive edge of the AWU clock signal
Once the switch is made, the internal RC is stopped
Reset the RC/AWU bit to enable the internal RC oscillator
Using a 4-bit counter, wait until 8 internal RC cycles have elapsed. The counter is
running on internal RC clock.
Wait till the AWU_FLAG is cleared (1AWU RC cycle) and the RC_FLAG is set (2 RC
cycles)
The switch to the internal RC clock is made at the positive edge of the internal RC clock
signal
Once the switch is made, the AWU RC is stopped
pins as close as possible to the ST7 device.
12):
Doc ID 13562 Rev 3
Section 14.1: Option bytes on page
DD
and V
for more information on the frequency
SS
pins and also between the V
173).
ST7LITE49M
DDA
and