PIC18F4550-I/P Microchip Technology Inc., PIC18F4550-I/P Datasheet - Page 174

• Manufacturer Part Number: PIC18F4550-I/P
• Description: 40 PIN, 32 KB FLASH, 2048 RAM, FS-USB 2.0
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4550-I/P

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 12 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 34
• Interface: I2C/SPI/UART/USART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F2455/2550/4455/4550
The BDnSTAT byte of the BDT should always be the
last byte updated when preparing to arm an endpoint.
The SIE will clear the UOWN bit when a transaction
has completed. The only exception to this is when KEN
is enabled and/or BSTALL is enabled.
No hardware mechanism exists to block access when
the UOWN bit is set. Thus, unexpected behavior can
occur if the microcontroller attempts to modify memory
when the SIE owns it. Similarly, reading such memory
may produce inaccurate data until the USB peripheral
returns ownership to the microcontroller.
17.4.1.2
When UOWN = 0, the microcontroller core owns the
BD. At this point, the other seven bits of the register
take on control functions.
The Keep Enable bit, KEN (BDnSTAT<5>), determines
if a BD stays enabled. If the bit is set, once the UOWN
bit is set, it will remain owned by the SIE independent
of the endpoint activity. This prevents the USTAT FIFO
from being updated, as well as the transaction
complete interrupt from being set for the endpoint. This
feature should only be enabled when the Streaming
Parallel Port is selected as the data I/O channel instead
of USB RAM.
The
(BDnSTAT<4>), controls the SIE’s automatic address
increment function. Setting INCDIS disables the
auto-increment of the buffer address by the SIE for
each byte transmitted or received. This feature should
only be enabled when using the Streaming Parallel
Port, where each data byte is processed to or from the
same memory location.
The
(BDnSTAT<3>), controls data toggle parity checking.
Setting DTSEN enables data toggle synchronization by
TABLE 17-3:
DS39632C-page 172
DATA0
DATA1
DATA0
DATA1
Either
Either, with error
Legend: x = don’t care
OUT Packet
from Host
Data
Address
BDnSTAT Register (CPU Mode)
Toggle
Increment
EFFECT OF DTSEN BIT ON ODD/EVEN (DATA0/DATA1) PACKET RECEPTION
Sync
DTSEN
BDnSTAT Settings
1
1
1
1
0
x
Disable
Enable
DTS
0
0
1
1
x
x
bit,
bit,
DTSEN
INCDIS
Handshake
Preliminary
ACK
ACK
ACK
ACK
ACK
NAK
Device Response after Receiving Packet
UOWN
the SIE. When enabled, it checks the data packet’s par-
ity against the value of DTS (BDnSTAT<6>). If a packet
arrives with an incorrect synchronization, the data will
essentially be ignored. It will not be written to the USB
RAM and the USB transfer complete interrupt flag will
not be set. The SIE will send an ACK token back to the
host to Acknowledge receipt, however. The effects of
the DTSEN bit on the SIE are summarized in
Table 17-3.
The Buffer Stall bit, BSTALL (BDnSTAT<2>), provides
support for control transfers, usually one-time stalls on
Endpoint 0. It also provides support for the
SET_FEATURE/CLEAR_FEATURE commands speci-
fied in Chapter 9 of the USB specification; typically,
continuous STALLs to any endpoint other than the
default control endpoint.
The BSTALL bit enables buffer stalls. Setting BSTALL
causes the SIE to return a STALL token to the host if a
received token would use the BD in that location. The
EPSTALL bit in the corresponding UEPn control regis-
ter is set and a STALL interrupt is generated when a
STALL is issued to the host. The UOWN bit remains set
and the BDs are not changed unless a SETUP token is
received. In this case, the STALL condition is cleared
and the ownership of the BD is returned to the
microcontroller core.
The BD9:BD8 bits (BDnSTAT<1:0>) store the two most
significant digits of the SIE byte count; the lower 8 digits
are stored in the corresponding BDnCNT register. See
Section 17.4.2
information.
0
1
0
1
0
1
TRNIF
1
0
1
0
1
0
“BD
BDnSTAT and USTAT Status
© 2006 Microchip Technology Inc.
Byte
Not Updated
Not Updated
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Updated
Updated
Updated
Count”
for
more