PIC24FJ256GB210-I/PT Microchip Technology Inc., PIC24FJ256GB210-I/PT Datasheet - Page 239

• Manufacturer Part Number: PIC24FJ256GB210-I/PT
• Description: 100 TQFP 12x12x1mm TRAY, 16-bit, 256KB Flash, 96K RAM, USB
• Manufacturer: Microchip Technology Inc.

Specifications of PIC24FJ256GB210-I/PT

• A/d Inputs: 24 Channel, 10-bit
• Comparators: 3
• Cpu Speed: 16 MIPS
• Eeprom Memory: 0 Bytes
• Input Output: 84
• Interface: I2C/SPI/UART/USART/USB
• Memory Type: Flash
• Number Of Bits: 16
• Package Type: 100-pin TQFP
• Programmable Memory: 256K Bytes
• Ram Size: 98K Bytes
• Speed: 32 MHz
• Temperature Range: –40 to 85 °C
• Timers: 5-16-bit
• Voltage, Range: 2.2-3.6 V
• Lead Free Status / Rohs Status: RoHS Compliant part

18.2
Endpoint buffer control is handled through a structure
called the Buffer Descriptor Table (BDT). This provides
a flexible method for users to construct and control
endpoint buffers of various lengths and configurations.
The BDT can be located in any available, 512-byte
aligned block of data RAM. The BDT Pointer
(U1BDTP1) contains the upper address byte of the
BDT and sets the location of the BDT in RAM. The user
must set this pointer to indicate the table’s location.
The BDT is composed of Buffer Descriptors (BDs)
which are used to define and control the actual buffers
in the USB RAM space. Each BD consists of two, 16-bit
“soft” (non-fixed-address) registers, BDnSTAT and
BDnADR, where n represents one of the 64 possible
BDs (range of 0 to 63). BDnSTAT is the status register
for BDn, while BDnADR specifies the starting address
for the buffer associated with BDn.
FIGURE 18-8:
 2010 Microchip Technology Inc.
Note:
Total BDT Space:
Note:
PPB<1:0> = 00
No Ping-Pong
128 Bytes
Buffers
USB Buffer Descriptors and
the BDT
Since BDnADR is a 16-bit register, only
the first 64 Kbytes of RAM can be
accessed by the USB module.
Memory area is not shown to scale.
EP0 RX
Descriptor
EP0 TX
Descriptor
EP1 RX
Descriptor
EP1 TX
Descriptor
EP15 TX
Descriptor
BDT MAPPING FOR ENDPOINT BUFFERING MODES
Ping-Pong Buffer
Total BDT Space:
PPB<1:0> = 01
on EP0 OUT
132 Bytes
EP0 RX Even
Descriptor
EP0 RX Odd
Descriptor
EP0 TX
Descriptor
EP1 RX
Descriptor
EP1 TX
Descriptor
EP15 TX
Descriptor
PIC24FJ256GB210 FAMILY
Ping-Pong Buffers
Total BDT Space:
PPB<1:0> = 10
on all EPs
256 Bytes
Depending on the endpoint buffering configuration
used, there are up to 64 sets of Buffer Descriptors, for
a total of 256 bytes. At a minimum, the BDT must be at
least 8 bytes long. This is because the “USB 2.0 OTG
Specification” mandates that every device must have
Endpoint 0 with both input and output for initial setup.
Endpoint mapping in the BDT is dependent on three
variables:
• Endpoint number (0 to 15)
• Endpoint direction (RX or TX)
• Ping-pong settings (U1CNFG1<1:0>)
Figure 18-8 illustrates how these variables are used to
map endpoints in the BDT.
In Host mode, only Endpoint 0 Buffer Descriptors are
used. All transfers utilize the Endpoint 0 Buffer Descrip-
tor and Endpoint Control register (U1EP0). For received
packets, the attached device’s source endpoint is
indicated by the value of ENDPT<3:0> in the USB status
register (U1STAT<7:4>). For transmitted packets, the
attached device’s destination endpoint is indicated by
the value written to the Token register (U1TOK).
EP0 RX Even
Descriptor
EP0 RX Odd
Descriptor
EP0 TX Even
Descriptor
EP0 TX Odd
Descriptor
EP1 RX Even
Descriptor
EP1 RX Odd
Descriptor
EP1 TX Even
Descriptor
EP1 TX Odd
Descriptor
EP15 TX Odd
Descriptor
Ping-Pong Buffers
Total BDT Space:
on all other EPs
PPB<1:0> = 11
except EP0
248 Bytes
DS39975A-page 239
EP0 RX
Descriptor
EP0 TX
Descriptor
EP1 RX Even
Descriptor
EP1 RX Odd
Descriptor
EP1 TX Even
Descriptor
EP1 TX Odd
Descriptor
EP15 TX Odd
Descriptor