Fast AMBA Peripherals
12-58
GMS30C7201 Data Sheet
Device Controller
The Device Controller contains a state machine that understands the USB protocol.
The (SIE) provides the Device Controller with the type of packet, address value,
endpoint value, and data stream for each incoming packet. The Device Controller then
checks to see if the packet is targeted to the device by comparing the address/endpoint
values with internal registers that were loaded with address and endpoint values during
the USB enumeration process. Assuming the address/endpoint is a match, the Device
Controller then interprets the packet. Data is passed on to the endpoint for all packets
except SETUP packets, which are handled specially. Data toggle bits (DATA0 and
DATA1 as defined by the USB spec) are maintained by the Device Controller. For IN
data packets (device to host) the Device Controller sends either the maximum number
of bytes in a packet or the number of bytes available from the endpoint. All packets are
acknowledged as per the spec. For SETUP packets, the incoming data is extracted into
the relevant internal fields, and then the appropriate action is carried out.
Table 12-36:
Supported Setup Requests
lists the types of setup operations that are supported.
Start of Frame
The Start of Frame logic generates a pulse whenever either the incoming Start of
Frame (SOF) packet arrives or approximately 1 ms after it the last one arrived. This
allows an isochronous endpoint to stay in sync even if the SOF packet has been
garbled.
12.10.4Endpoint FIFOs (Rx,Tx)
Each endpoint FIFO has the specific number of FIFO depth according to data transfer
rate. In case of maximum packet size for bulk transfer is 32 bytes that is supported in
USBD. Each FIFO generates dataready signals (means FIFO not full or FIFO not
empty) to AMBA I/F and causes AMBA I/F to produce DMAC request signals. It
contains the control logic for transferring 4 bytes at a read/write strobe generated by
AMBA to obtain better efficiency of AMBA bus.
Setup Request
Value
Supported
Get Status
0
Device, Interface, Endpoint
Clear Feature
1
Endpoints Only
Set Feature
3
Not supported
Set Address
5
Device
Get Descriptor
6
Device
Set Descriptor
7
Not supported
Get Configuration
8
Device
Set Configuration
9
Device
Get Interface
10
Not supported
Set Interface
11
Not supported
Synch Frame
12
Not supported
Table 12-36: Supported Setup Requests