
Communication Processor Module
16-368
MPC823 USER’S MANUAL
MOTOROLA
USB
COMMUNICATION
16
PROCESSOR
MODULE
16.10.8.8 USB EVENT REGISTER. The 16-bit, memory-mapped USB event register
(USBER) is used to generate interrupt events and report events recognized by the USB
channel. When an event is recognized, the USB sets the corresponding bit in the USBER.
Interrupts generated by this register may be masked in the USBMR. A bit is cleared by
writing a one (writing a zero has no effect) and more than one bit can be cleared at a time.
All unmasked bits must be cleared before the communication processor module will clear
the internal interrupt request.
Bits 0–5—Reserved
These bits are reserved and should be set to 0.
RESET—Reset Condition Detected
This bit indicates that the USB reset condition has been asserted.
IDLE—IDLE Status Changed
This bit indicates that a change in the status of the serial line was detected. The real time
suspend status is reflected in the USBS register.
TXEx—TX Error
This bit indicates that an error occurred during transmission for endpoint x (packet not
acknowledged or underrun).
SOF—Start of Frame
This bit indicates that a start-of-frame packet was received. The packet is stored in the
FRAME_N parameter RAM entry
BSY—Busy Condition
This bit indicates that received data has been discarded due to a lack of buffers. This bit is
set after the first character is received for which there is no receive buffer available.
TXB—TX Buffer
This bit indicates that a buffer has been transmitted. It is set once the transmit data of the
last character in the buffer was written to the transmit FIFO (if L=0) or after the last character
was transmitted on the line (if L=1).
RXB—RX Buffer
This bit indicates that a buffer has been received. It is set after the last character has been
written to the receive buffer and the RX buffer descriptor is closed.
USBER
BIT
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
FIELD
RESERVED
RESET
IDLE
TXE3
TXE2
TXE1
TXE0
SOF
BSY
TXB
RXB
RESET
0
0000000000
R/W
R/W
ADDR
(IMMR & 0
xFFFF0000) + 0xA10