30-26
MPC860 PowerQUICC UserÕs Manual
MOTOROLA
Part V. The Communications Processor Module
Table 30-13 describes receive commands issued to the CPCR.
30.4.8 Handling Errors in the SMC Transparent Controller
The SMC uses BDs and the SMCE to report message transmit and receive errors.
30.4.9 SMC Transparent Receive BD (RxBD)
Using BDs, the CP reports information about the received data for each buffer and closes
the current buffer, generates a maskable interrupt, and starts to receive data into the next
buffer after one of the following events:
¥
An overrun error occurs.
¥
A full receive buffer is detected.
¥
The
ENTER
HUNT
MODE
command is issued.
Figure 30-13 shows the SMC transparent RxBD format.
Table 30-13. SMC Transparent Receive Commands
Command Description
ENTER
HUNT
MODE
Forces the SMC to close the current receive BD if it is in use and to use the next BD for subsequent
data. If the SMC is not receiving data, the buffer is not closed. Additionally, this command causes the
receiver to wait for a resynchronization before reception resumes.
CLOSE
RXBD
Forces the SMC to close the current receive BD if it in use and to use the next BD in the list for
subsequent received data. If the SMC is not in the process of receiving data, no action is taken.
i
NIT
RX
PARAMETERS
Initializes receive parameters in this serial channel to reset state. Use only if the receiver is disabled.
The
INIT
TX
AND
RX
PARAMETERS
command resets receive and transmit parameters.
Table 30-14. SMC Transparent Error Conditions
Error
Descriptions
Underrun The channel stops sending the buffer, closes it, sets UN in the BD, and generates a TXE interrupt if it is
enabled. The channel resumes sending after a
RESTART
TRANSMIT
command. Underrun cannot occur
between frames.
Overrun
The SMC maintains an internal FIFO for receiving data. If the buffer is in external memory, the CP begins
programming the SDMA channel when the Þrst character is received into the FIFO. If a FIFO overrun
occurs, the SMC writes the received data character over the previously received character. The previous
character and its status bits are lost. Then the channel closes the buffer, sets OV in the BD, and generates
the RX interrupt if it is enabled. Reception continues as normal.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
E
Ñ
W
I
Ñ
CM
Ñ
OV
Ñ
2
Data Length
4
Rx Buffer Pointer
6
Figure 30-13. SMC Transparent Receive BD (RxBD)
Содержание MPC860 PowerQUICC
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