UPSD3422 datasheet(287/293 Pages) STMICROELECTRONICS

287 / 293 page

uPSD34xx

Important notes

287/293

Important notes

The following sections describe the limitations that apply to the uPSD34xx devices and the

differences between revision A and B silicon.

34.1

USB interrupts with idle mode

Description

An interrupt generated by a USB related event does not bring the MCU out of idle mode for

processing.

Impact On Application

Idle mode cannot be used with USB.

Workaround

Revision A - None identified at this time.

Revision B - Corrected in silicon so that a USB interrupt that occurs will bring the MCU out of

idle mode.

34.2

USB Reset Interrupt

Description

When the MCU clock prescaler is set to a value other than fMCU = fOSC (no division), a reset

signal on the USB does not cause a USB interrupt to be generated.

Impact On Application

An MCU clock other than that equal to the frequency of the oscillator cannot be used.

Workaround

Revision A - The CPUPS field in the CCON0 register must be set to 000b (default after

reset). The 3400 USB firmware examples set CCON0 register to 000b.

Revision B - Corrected in silicon so that when an MCU clock prescaler is used, a reset

signal on the USB does generate an interrupt.

34.3

USB Reset

Description

A USB reset does not reset the USB SIE's registers.

Impact On Application

A USB reset does not reset the USB SIE's registers as does a power-on or hardware reset.

UPSD3422 Datasheet(PDF) 287 Page - STMicroelectronics