PIC16LF1454 Datasheet, PDF (319/418 Pages) Microchip Technology – 14/20-Pin Flash, 8-Bit USB Microcontrollers with XLP Technology

26.5.1 USB INTERRUPT STATUS (UIR)
REGISTER
The USB Interrupt Status register (Register 26-7) con-
tains the flag bits for each of the USB Status interrupt
sources. Each of these sources has a corresponding
interrupt enable bit in the UIE register. All of the USB
status flags are ORed together to generate the USBIF
interrupt flag for the microcontroller's interrupt funnel.
Once an interrupt bit has been set by the SIE, it must
be cleared by software. The flag bits can also be set in
software which can aid in firmware debugging.
Note:
All status flags in the UIR register should
be resolved and cleared before the USBIF
bit is cleared.
26.5.1.1 Bus Activity Detect Interrupt Bit
(ACTVIF)
The ACTVIF bit cannot be cleared immediately after the
USB module wakes up from Suspend or while the USB
module is suspended. A few clock cycles are required to
synchronize the internal hardware state machine before
the ACTVIF bit can be cleared by firmware. Clearing the
ACTVIF bit in firmware before the internal hardware is
synchronized may not have an effect on the value of
ACTVIF. The USB module may not be immediately oper-
ational after clearing the SUSPND bit if using the 48 MHz
PLL source because the PLL will require time to lock.
The application code should clear the ACTVIF flag as
shown in Example 26-1.
Only one ACTVIF interrupt is generated when resum-
ing from the USB bus Idle condition. If user firmware
clears the ACTVIF bit, even when there is continuous
bus traffic, the bit will not become set again until after a
IDLEIF condition occurs. Bus traffic must cease long
enough to generate another IDLEIF condition before
another ACTVIF interrupt can be generated.
EXAMPLE 26-1: CLEARING ACTVIF BIT
(UIR<2>)
Assembly:
BCF
LOOP:
BTFSS
BRA
BCF
BRA
DONE:
UCON, SUSPND
UIR, ACTVIF
DONE
UIR, ACTVIF
LOOP
C:
UCONbits.SUSPND = 0;
while (UIRbits.ACTVIF) { UIRbits.ACTVIF = 0; }
PIC16(L)F1454/5/9
26.5.2 USB INTERRUPT ENABLE
REGISTER (UIE)
The USB Interrupt Enable register (Register 26-8) con-
tains the enable bits for the USB Status interrupt
sources. Setting any of these bits will enable the
respective interrupt source in the UIR register.
The values in this register only affect the propagation of
an interrupt condition to the microcontroller's interrupt
logic. The flag bits are set by their interrupt conditions,
allowing them to be polled and serviced without actu-
ally generating an interrupt.
26.5.3 USB ERROR INTERRUPT STATUS
REGISTER (UEIR)
The USB Error Interrupt Status register (Register 26-9)
contains the flag bits for each of the error sources
within the USB peripheral. Each of these sources is
enabled by a corresponding bit in the UEIE register. All
of the USB error flags are ORed together to generate
the USB Error Interrupt Flag (UERRIF) at the top level
of the interrupt logic.
Each error bit is set as soon as the error condition is
detected. Thus, the interrupt will typically not corre-
spond with the end of a token being processed.
Once an interrupt bit has been set by the SIE, it must
be cleared by software.
Note:
All status flags in the UEIR register should
be resolved and cleared before the
UERRIF bit is cleared.
26.5.4 USB INTERRUPT (UEIE) ENABLE
REGISTER
The USB Error Interrupt Enable register (Register 26-10)
contains the enable bits for each of the USB error inter-
rupt sources. Setting any of these bits will enable the
respective error interrupt source in the UEIR register. If
enabled, the UERRIF bit of the UIR register will be set
when any USB error interrupt is set.
As with the UIE register, the enable bits only affect the
propagation of an interrupt condition to the
microcontroller's interrupt logic. The flag bits are set by
their interrupt conditions, allowing them to be polled
and serviced without actually generating an interrupt.
 2012 Microchip Technology Inc.
Preliminary
DS41639A-page 319