RM0368 Datasheet, PDF (665/841 Pages) STMicroelectronics – This Reference manual targets application developers

RM0368
USB on-the-go full-speed (OTG_FS)
22.2.1
22.2.2
General features
The OTG_FS interface general features are the following:
• It is USB-IF certified to the Universal Serial Bus Specification Rev 2.0
• It includes full support (PHY) for the optional On-The-Go (OTG) protocol detailed in the
On-The-Go Supplement Rev 1.3 specification
– Integrated support for A-B Device Identification (ID line)
– Integrated support for host Negotiation Protocol (HNP) and Session Request
Protocol (SRP)
– It allows host to turn V_BUS off to conserve battery power in OTG applications
– It supports OTG monitoring of V_BUS levels with internal comparators
– It supports dynamic host-peripheral switch of role
• It is software-configurable to operate as:
– SRP capable USB FS Peripheral (B-device)
– SRP capable USB FS/LS host (A-device)
– USB On-The-Go Full-Speed Dual Role device
• It supports FS SOF and LS Keep-alives with
– SOF pulse PAD connectivity
– SOF pulse internal connection to timer2 (TIM2)
– Configurable framing period
– Configurable end of frame interrupt
• It includes power saving features such as system stop during USB Suspend, switch-off
of clock domains internal to the digital core, PHY and DFIFO power management
• It features a dedicated RAM of 1.25 Kbytes with advanced FIFO control:
– Configurable partitioning of RAM space into different FIFOs for flexible and
efficient use of RAM
– Each FIFO can hold multiple packets
– Dynamic memory allocation
– Configurable FIFO sizes that are not powers of 2 to allow the use of contiguous
memory locations
• It guarantees max USB bandwidth for up to one frame (1ms) without system
intervention
Host-mode features
The OTG_FS interface main features and requirements in host-mode are the following:
• External charge pump for V_BUS voltage generation.
• Up to 8 host channels (pipes): each channel is dynamically reconfigurable to allocate
any type of USB transfer.
• Built-in hardware scheduler holding:
– Up to 8 interrupt plus isochronous transfer requests in the periodic hardware
queue
– Up to 8 control plus bulk transfer requests in the non-periodic hardware queue
• Management of a shared RX FIFO, a periodic TX FIFO and a nonperiodic TX FIFO for
efficient usage of the USB data RAM.
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