mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 290

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

Software Architecture and Application Notes
An example FIFO configuration with a variety of endpoint types and packet sizes is shown
in Table 12-20.
12.4.4 Data Flow
The handling of the data flow to and from each endpoint can be divided between
isochronous and non-isochronous endpoints. Isochronous endpoints are designed to
transfer streaming data which is continuous and real-time in creation, delivery, and
consumption. The timely delivery of isochronous data is ensured at the expense of potential
transient losses in the data stream. In other words, any error in electrical transmission in not
corrected by hardware mechanisms such as retries. An example of streaming data is voice.
The other endpoint types transfer message based, or bursted data where integrity of the data
is more important than timely delivery.
12.4.4.1 Control, Bulk, and Interrupt Endpoints
The data flow for control, bulk, and interrupt endpoints can be handled the same way for all
3 types of endpoints. Control, bulk, and interrupt endpoints all support guaranteed data
delivery. If the host detects an error during the read of a packet from an IN endpoint, it
requests that the packet be resent from the device. The USB FIFO mechanism takes care of
this without interrupting the CPU. In a similar fashion, the USB FIFO mechanism keeps a
received packet from being read by the user until the control logic validates the packet for
transmission errors.
12-30
• The FIFO_ADDR field in the EPnCFG registers must be aligned to a boundary
• The FIFO space for an endpoint defined by FIFO_SIZE and FIFO_ADDR must not
Endpoint
Number
defined by the FIFO_SIZE field. For example, a FIFO with a size equal to 64 bytes
can have a starting address of 0, 64, 128, 192, 256, etc.
overlap with the FIFO space for any other endpoint with the same direction.
0
0
1
2
3
4
5
6
7
Endpoint
Direction
OUT
OUT
OUT
OUT
IN
IN
IN
IN
IN
Isochronous
Isochronous
Isochronous
Isochronous
Table 12-20. Example FIFO Setup
Endpoint
Interrupt
Control
Control
Type
Bulk
Bulk
MCF5272 User’s Manual
Max Packet
Size
300
300
17
64
32
8
8
5
5
FIFO Size
128
128
256
256
32
32
32
32
64
FIFO Starting
Address
480
384
384
256
256
448
416
0
0
0x020101C0
0x014101C0
0x014101A0
0x4B080000
0x4B080000
0x02010180
0x04420180
0x10040100
0x08040100
EPnCFG
Value
MOTOROLA