I/O Register Description of the Embedded Device Function
MC68HC08KH12A Data Sheet, Rev. 1.1
Freescale Semiconductor
97
9.5.4 USB Embedded Device Control Register 0 (DCR0)
T0SEQ — Embedded Device Endpoint 0 Transmit Sequence Bit
This read/write bit determines which type of data packet (DATA0 or DATA1) will be sent during the next
IN transaction directed at Endpoint 0. Toggling of this bit must be controlled by software. Reset clears
this bit.
1 = DATA1 Token active for next embedded device Endpoint 0 transmit
0 = DATA0 Token active for next embedded device Endpoint 0 transmit
DSTALL0 — Embedded Device Endpoint 0 Force Stall Bit
This read/write bit causes embedded device Endpoint 0 to return a STALL handshake when polled by
either an IN or OUT token by the host. The USB hardware clears this bit when a SETUP token is
received. Reset clears this bit.
1 = Send STALL handshake
0 = Default
TX0E — Embedded Device Endpoint 0 Transmit Enable
This read/write bit enables a transmit to occur when the USB Host controller sends an IN token to the
embedded device Endpoint 0. Software should set this bit when data is ready to be transmitted. It must
be cleared by software when no more embedded device Endpoint 0 data needs to be transmitted.
If this bit is 0 or the TXD0F is set, the USB will respond with a NAK handshake to any embedded device
Endpoint 0 IN tokens. Reset clears this bit.
1 = Data is ready to be sent
0 = Data is not ready. Respond with NAK
RX0E — Embedded Device Endpoint 0 Receive Enable
This read/write bit enables a receive to occur when the USB Host controller sends an OUT token to
the embedded device Endpoint 0. Software should set this bit when data is ready to be received. It
must be cleared by software when data cannot be received.
If this bit is 0 or the RXD0F is set, the USB will respond with a NAK handshake to any embedded device
Endpoint 0 OUT tokens. Reset clears this bit.
1 = Data is ready to be received
0 = Not ready for data. Respond with NAK
TP0SIZ3-TP0SIZ0 — Embedded Device Endpoint 0 Transmit Data Packet Size
These read/write bits store the number of transmit data bytes for the next IN token request for
embedded device Endpoint 0. These bits are cleared by reset.
Address: $004B
Bit 7
6
5
4
3
2
1
Bit 0
Read:
T0SEQ
DSTALL0
TX0E
RX0E
TP0SIZ3
TP0SIZ2
TP0SIZ1
TP0SIZ0
Write:
Reset:
0
0
0
0
0
0
0
0
Figure 9-19. USB Embedded Device Control Register 0 (DCR0)