Communication Processor Module
16-358 MPC823e REFERENCE MANUAL MOTOROLA
USB
COMMUNICATION
16
PROCESSOR MODULE
16.10.4.4 SOF TOKEN. When a start of frame (SOF) token packet is received, the USB
controller issues a SOF maskable interrupt and the frame number entry in the parameter
RAM is updated.
16.10.4.5 PRE TOKEN. The PRE token signals the hub that a low-speed transaction is
about to occur. The PRE token is only read by the hub. The USB controller ignores the PRE
token in slave mode. In host mode, the USB controller generates a full-speed PRE token
before any packet is sent to a low-speed peripheral.
16.10.5 USB Controller Parameter RAM Memory Map
The USB controller parameter RAM area begins at the USB base address. The area is used
for the general USB parameters. Notice that it is similar to the SCCx general-purpose
parameter RAM.
Table 16-34. USB Parameter RAM Memory Map
ADDRESS NAME WIDTH DESCRIPTION
USB Base + 00 EP0PTR Half Word Endpoint 0 Register
USB Base + 02 EP1PTR Half Word Endpoint 1 Register
USB Base + 04 EP2PTR Half-Word Endpoint 2 Register
USB Base + 06 EP3PTR Half Word Endpoint 3 Register
USB Base + 08 RSTATE Word RX Internal State
USB Base + 0C RPTR Word RX Internal Data Pointer
USB Base + 10 FRAME_N Half Word Frame Number
USB Base + 12 RBCNT Half-Word RX Internal Byte Count
USB Base + 14 RTEMP Word RX Temp
NOTE: You are only responsible for initializing the items in bold.
USB Base = (IMMR & 0xFFFF0000) + 0x3C00.
All references to registers in the parameter RAM table are actually implemented in the dual-port RAM
area as a memory-based register.
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