Freescale Semiconductor ColdFire MCF52210 - Manual (Page 249)

Universal Serial Bus, OTG Capable Controller
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 15-21
15.4.1.13 Status Register (STAT)
The Status Register reports the transaction status within the USB Module. When the ColdFire core has
received a TOK_DNE interrupt the Status Register should be read to determine the status of the previous
endpoint communication. The data in the status register is valid when the TOK_DNE interrupt bit is
asserted. The STAT register is actually a read window into a status FIFO maintained by the USB Module.
When the USB Module uses a BD, it updates the Status Register. If another USB transaction is performed
before the TOK_DNE interrupt is serviced, the USB Module stores the status of the next transaction in the
STAT FIFO. Thus the STAT register is actually a four byte FIFO that allows the ColdFire core to process
one transaction while the SIE is processing the next transaction. Clearing the TOK_DNE bit in the
INT_STAT register causes the SIE to update the STAT register with the contents of the next STAT value.
If the data in the STAT holding register is valid, the SIE immediately reasserts to TOK_DNE interrupt.
Figure 15-19 shows the STAT register.
IPSBAR
Offset:
0x1C_0090 (STAT)
Access: User read-only
7 6 5 4 3 2 1 0
R ENDP TX ODD Reserved Reserved
W
Reset: 0 0 0 0 0 0 0 0
Figure 15-19. Status Register
Table 15-23. STAT Field Descriptions
Field Description
7 - 5
ENDP[3:0]
This four-bit field encodes the endpoint address that received or transmitted the previous token. This allows the
ColdFire core to determine which BDT entry was updated by the last USB transaction.
3
TX
Transmit Indicator
0
The most recent transaction was a Receive operation
1 The most recent transaction was a Transmit operation
2
ODD
this bit is set if the last Buffer Descriptor updated was in the odd bank of the BDT.
1 - 0 Reserved