Designer Reference Manual
USB08 Evaluation Board
66
Universal Serial Bus (USB) Interface
MOTOROLA
Universal Serial Bus (USB) Interface
configured as an IN or as an OUT endpoint. The reference design uses
this endpoint as an OUT endpoint, to do data transfers to the MCU.
provides an overview of the endpoint configuration.
Some adjustments in the control registers of the USB module are
necessary for the configuration of the endpoints. While EP0 is always
active as a control endpoint, the bit ENABLE1 in control register 3
(UCR3) has to be set to activate the endpoint EP1. Likewise, the bit
ENABLE2 has to be set for activation of the endpoint EP2.
However, the activation of the endpoints EP1 and EP2 takes place not
in the initialization routine initUSB(), but only after the device receives a
USB reset.
Table 4-2. MC68HC908JB8 Endpoint Configuration
Endpoint
Type
Direction
Function
EP0
Control
IN/OUT
Device configuration
EP1
Interrupt
IN
Data transfer to the host
EP2
Interrupt
OUT
(a)
a. Alternatively as IN configurable, this option is not used here.
Data transfer to the device
Bit 7
6
5
4
3
2
1
Bit 0
Read:
TX1ST
0
OSTALL0
ISTALL0
0
PULLEN ENABLE2 ENABLE1
Write:
TX1STR
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 4-2. USB Control Register 3 (UCR3)
