Usb endpoint – Freescale Semiconductor MCF5480 User Manual
Page 909
Memory Map/Register Definition
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor
29-35
29.2.5.2
USB Endpoint n Interrupt Status Register (EPnISR)
The EPnISR monitors the status of a specific endpoint and generates a CPU interrupt each time a
monitored event occurs.
An interrupt, once set, remains set until cleared by writing a 1 to the corresponding bit. Interrupts do not
clear automatically if the event that caused them goes away (for example, if an endpoint FIFO is emptied
and then filled with no intervention from software, both EMT and FU would be set). Writing a 0 has no
effect.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
0
0
0
0
BYTECNT
W
Reset
Uninitialized
0
0
0
0
0
0
0
0
0
0
0
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
DIR
0
0
0
0
0
W
FLUSH RST
Reset
Uninitialized
0
Uninitialized
0
0
Reg
Addr
MBAR + 0xB440 (EP0STAT); 0xB470 (EP1STAT); 0xB4A0 (EP2STAT); 0xB4D0 (EP3STAT);
0xB500 (EP4STAT); 0xB530 (EP5STAT); 0xB560 (EP6STAT)
Figure 29-41. USB Endpoint n Status and Control Register (EPnSTAT)
Table 29-36. EPnSTAT Field Descriptions
Bits
Name
Description
31–28
—
Reserved, should be cleared.
27–16
BYTECNT
Byte count. This field indicates the number of bytes currently stored in the associated FIFO. This
value is a "live" count that does not differentiate between data that is from accepted or
not-yet-accepted data packets. Thus, the value may jump around in cases where packets are
discarded or retransmitted.
15–8
—
Reserved, should be cleared.
7
DIR
Direction. This is the transfer direction. This bit also determines the direction of the endpoint FIFO.
This bit should be set appropriately before responding to transfer requests from the host.
0 OUT Endpoint (from host to device).
1 IN Endpoint (from device to host).
6–2
—
Reserved, should be cleared.
1
FLUSH
Flush. This write only bit causes the associated FIFO to be flushed to its empty state. All FIFO
pointers will be reset to the empty state while FIFO configuration registers (USB_EPn_FCR) retain
their values.
0 Do nothing.
1 Initiate flush operation.
0
RST
Reset. This write only bit causes the associated FIFO to be reset. All configuration data will be lost
and the FIFO pointers will reset to the empty state.
0 Do nothing.
1 Initiate reset operation.