PIC18F-LF1XK50 MICROCHIP [Microchip Technology], PIC18F-LF1XK50 Datasheet - Page 252

• Manufacturer Part Number: PIC18F-LF1XK50
• Description: 20-Pin USB Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F/LF1XK50
22.2
The operation of the USB module is configured and
managed through three control registers. In addition, a
total of 14 registers are used to manage the actual USB
transactions. The registers are:
• USB Control register (UCON)
• USB Configuration register (UCFG)
• USB Transfer Status register (USTAT)
• USB Device Address register (UADDR)
• Frame Number registers (UFRMH:UFRML)
• Endpoint Enable registers 0 through 7 (UEPn)
22.2.1
The USB Control register
needed to control the module behavior during transfers.
The register contains bits that control the following:
• Main USB Peripheral Enable
• Ping-Pong Buffer Pointer Reset
• Control of the Suspend mode
• Packet Transfer Disable
REGISTER 22-1:
DS41350E-page 252
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
Note 1:
U-0
—
USB Status and Control
This bit cannot be set if the USB module does not have an appropriate clock source.
USB CONTROL REGISTER (UCON)
Unimplemented: Read as ‘0’
PPBRST: Ping-Pong Buffers Reset bit
1 = Reset all Ping-Pong Buffer Pointers to the Even Buffer Descriptor (BD) banks
0 = Ping-Pong Buffer Pointers not being reset
SE0: Live Single-Ended Zero Flag bit
1 = Single-ended zero active on the USB bus
0 = No single-ended zero detected
PKTDIS: Packet Transfer Disable bit
1 = SIE token and packet processing disabled, automatically set when a SETUP token is received
0 = SIE token and packet processing enabled
USBEN: USB Module Enable bit
1 = USB module and supporting circuitry enabled (device attached)
0 = USB module and supporting circuitry disabled (device detached)
RESUME: Resume Signaling Enable bit
1 = Resume signaling activated
0 = Resume signaling disabled
SUSPND: Suspend USB bit
1 = USB module and supporting circuitry in Power Conserve mode, SIE clock inactive
0 = USB module and supporting circuitry in normal operation, SIE clock clocked at the configured rate
Unimplemented: Read as ‘0’
PPBRST
R/W-0
UCON: USB CONTROL REGISTER
(Register
C = Clearable bit
W = Writable bit
‘1’ = Bit is set
SE0
22-1) contains bits
R-x
PKTDIS
R/C-0
(1)
Preliminary
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
USBEN
R/W-0
In addition, the USB Control register contains a status
bit, SE0 (UCON<5>), which is used to indicate the
occurrence of a single-ended zero on the bus. When
the USB module is enabled, this bit should be moni-
tored to determine whether the differential data lines
have come out of a single-ended zero condition. This
helps to differentiate the initial power-up state from the
USB Reset signal.
The overall operation of the USB module is controlled
by the USBEN bit (UCON<3>). Setting this bit activates
the module and resets all of the PPBI bits in the Buffer
Descriptor Table to ‘0’. This bit also activates the inter-
nal pull-up resistors, if they are enabled. Thus, this bit
can be used as a soft attach/detach to the USB.
Although all Status and control bits are ignored when
this bit is clear, the module needs to be fully preconfig-
ured prior to setting this bit. This bit cannot be set until
the USB module is supplied with an active clock
source. If the PLL is being used, it should be enabled
at least two milliseconds (enough time for the PLL to
lock) before attempting to set the USBEN bit.
(1)
RESUME
R/W-0
 2010 Microchip Technology Inc.
x = Bit is unknown
SUSPND
R/W-0
U-0
—
bit 0