MC9S08JM60_09 Datasheet, PDF (317/388 Pages) Freescale Semiconductor, Inc – HCS08 Microcontrollers

USB RAM
Offset
0x00
0x1D
0x1E
0x1F
0x20
Universal Serial Bus Device Controller (S08USBV1)
Table 17-21. USB RAM Organization
USB RAM Description of Contents
BDT
Endpoint 0 IN
Endpoint 0, OUT
Endpoint 1
Endpoint 2
Endpoint 3
Endpoint 4
Endpoint 5, Buffer EVEN
Endpoint 5, Buffer ODD
Endpoint 6, Buffer EVEN
Endpoint 6, Buffer ODD
RESERVED
RESERVED
USB RAM available for endpoint buffers
0xFF
When the USB module receives a USB token on an enabled endpoint, it interrogates the BDT. The USB
module reads the corresponding endpoint BD entry and determines if it owns the BD and corresponding
data buffer.
17.4.2.3 Buffer Descriptor Formats
The buffer descriptors (BDs) are groups of registers that provide endpoint buffer control information for
the USB module and the MCU. The BDs have different meanings based on who is reading the BD in
memory.
The USB module uses the data stored in the BDs to determine:
• Who owns the buffer in system memory
• Data0 or Data1 PID
• Release Own upon packet completion
• Data toggle synchronization enable
• How much data to be transmitted or received
• Where the buffer resides in the buffer RAM.
The microcontroller uses the data stored in the BDs to determine:
• Who owns the buffer in system memory
• Data0 or Data1 PID
• The received TOKEN PID
MC9S08JM60 Series Data Sheet, Rev. 3
Freescale Semiconductor
317