Datasheet

Functional overview STM32L072xx
36/149 DocID027100 Rev 4
3.17.5 Universal serial bus (USB)
The STM32L072xx embed 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.
3.18 Clock recovery system (CRS)
The STM32L072xx embed a special block which allows automatic trimming of the internal
48 MHz oscillator to guarantee its optimal accuracy over the whole device operational
range. This automatic trimming is based on the external synchronization signal, which could
be either derived from USB SOF signalization, from LSE oscillator, from an external signal
on CRS_SYNC pin or generated by user software. For faster lock-in during startup it is also
possible to combine automatic trimming with manual trimming action.
3.19 Cyclic redundancy check (CRC) calculation unit
The CRC (cyclic redundancy check) calculation unit is used to get a CRC code using a
configurable generator polynomial value and size.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the EN/IEC 60335-1 standard, they offer a means of
verifying the Flash memory integrity. The CRC calculation unit helps compute a signature of
the software during runtime, to be compared with a reference signature generated at
linktime and stored at a given memory location.
3.20 Serial wire debug port (SW-DP)
An Arm SW-DP interface is provided to allow a serial wire debugging tool to be connected to
the MCU.
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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