Datasheet

DocID027096 Rev 2 35/137
STM32L073xx Functional overview
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Only a 32.768 kHz clock (LSE) is needed to allow LPUART communication up to 9600
baud. Therefore, even in Stop mode, the LPUART can wait for an incoming frame while
having an extremely low energy consumption. Higher speed clock can be used to reach
higher baudrates.
LPUART interface can be served by the DMA controller.
3.18.4 Serial peripheral interface (SPI)/Inter-integrated sound (I2S)
Up to two SPIs are able to communicate at up to 16 Mbits/s in slave and master modes in
full-duplex and half-duplex communication modes. The 3-bit prescaler gives 8 master mode
frequencies and the frame is configurable to 8 bits or 16 bits. The hardware CRC
generation/verification supports basic SD Card/MMC modes.
One standard I2S interfaces (multiplexed with SPI2) is available. It can operate in master or
slave mode, and can be configured to operate with a 16-/32-bit resolution as input or output
channels. Audio sampling frequencies from 8 kHz up to 192 kHz are supported. When the
I2S interfaces is configured in master mode, the master clock can be output to the external
DAC/CODEC at 256 times the sampling frequency.
The SPIs can be served by the DMA controller.
Refer to Table 14 for the differences between SPI1 and SPI2.
3.18.5 Universal serial bus (USB)
The STM32L073xx embeds a full-speed USB device peripheral compliant with the USB
specification version 2.0. The internal USB PHY supports USB FS signaling, embedded DP
pull-up and also battery charging detection according to Battery Charging Specification
Revision 1.2. The USB interface implements a full-speed (12 Mbit/s) function interface with
added support for USB 2.0 Link Power Management. It has software-configurable endpoint
setting with packet memory up to 1 KB and suspend/resume support. It requires a precise
48 MHz clock which can be generated from the internal main PLL (the clock source must
use a HSE crystal oscillator) or by the internal 48 MHz oscillator in automatic trimming
mode. The synchronization for this oscillator can be taken from the USB data stream itself
(SOF signalization) which allows crystal-less operation.
Table 14. SPI/I2S implementation
SPI features
(1)
1. X = supported.
SPI1 SPI2
Hardware CRC calculation X X
I2S mode - X
TI mode X X
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