Datasheet

Universal Serial Bus Module (USB)
I/O Registers
MC68HC908JB8•MC68HC08JB8•MC68HC08JT8 — Rev. 2.3 Technical Data
Freescale Semiconductor Universal Serial Bus Module (USB) 151
9.8.9 USB Control Register 4
USB control register 4 directly controls the USB data pins D+ and D–. If
the FUSBO bit, and the USBEN bit of the USB address register
(UADDR) are set, the output buffers of the USB modules are enabled
and the corresponding levels of the USB data pins D+ and D– are equal
to the values set by the FDP and the FDM bits.
FUSBO — Force USB Output
This read/write bit enables the USB output buffers.
1 = Enables USB output buffers
0 = USB module in normal operation
FDP — Force D+
This read/write bit determinates the output level of D+.
1 = D+ at output high level
0 = D+ at output low level
FDM — Force D–
This read/write bit determinates the output level of D–.
1 = D– at output high level
0 = D– at output low level
NOTE: Customers must be very careful when setting the UCR4 register. When
the FUSBO and the USBEN bits are set, the USB module is in output
mode and it will not recognize any USB signals including the USB reset
signal. The UCR4 register is used for some special applications.
Customers are not normally expected to use this register.
Address: $001B
Bit 7654321Bit 0
Read:
0 0 0 0 0
FUSBO FDP FDM
Write:
Reset:00000000
= Unimplemented
Figure 9-23. USB Control Register 4 (UCR4)