Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 787

Table 28-4 describes receive commands.
Command
After hardware or software is reset and the channel is enabled, the channel is in receive enable
ENTER HUNT
mode and uses the first BD in the table.
MODE
current frame and enter hunt mode where the transparent controller waits for the synchronization
sequence. After receiving the command, the current buffer is closed. Further data reception uses
the next BD.
Forces the SCC to close the RxBD if it is being used and to use the next BD for any subsequently
CLOSE RXBD
received data. If the SCC is not receiving data, no action is taken by this command.
Initializes all receive parameters in this serial channel parameter RAM to reset state. Issue only
INIT RX
when the receiver is disabled.
PARAMETERS
28.7 Handling Errors in the Transparent Controller
The SCC reports message reception and transmission errors using the channel buffer descriptors, the error
counters, and SCCE. Table 28-5
Error
Transmitter When this occurs, the channel stops sending the buffer, closes it, sets TxBD[UN], and generates a
Underrun TXE interrupt if it is enabled. Transmission resumes after a
Underrun occurs after a transmit frame for which TxBD[L] was not set. In this case, only SCCE[TXE]
is set. Underrun cannot occur between transparent frames.
CTS Lost During When this occurs, the channel stops sending the buffer, closes it, sets TxBD[CT], and generates the
Message TXE interrupt if it is enabled. The channel resumes sending after
Transmission
Table 28-6 describes receive errors.
Error
Overrun The SCC maintains a receive FIFO. The CPM starts programming the SDMA channel if the buffer
is in external memory and updating the CRC when 8 or 32 bits are received in the FIFO as
determined by GSMR_H[RFW]. If a FIFO overrun occurs, the SCC writes the received byte over the
previously received byte. The previous character and its status bits are lost. Afterwards, the channel
closes the buffer, sets OV in the BD, and generates the RXB interrupt if it is enabled. The receiver
immediately enters hunt mode.
CD Lost During When this occurs, the channel stops receiving messages, closes the buffer, sets RxBD[CD], and
Message generates the RXB interrupt if it is enabled. This error has highest priority. The rest of the message
Reception is lost, and no other errors are checked in the message. The receiver immediately enters hunt mode.
28.8 Transparent Mode and the PSMR
The protocol-specific mode register (PSMR) is not used by the transparent controller because all
transparent mode selections are made in the GSMR. If only half of an SCC (transmitter or receiver) is
Freescale Semiconductor
Table 28-4. Receive Commands
INIT TX AND RX PARAMETERS
describes transmit errors.
Table 28-5. Transmit Errors
Table 28-6. Receive Errors
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Description
forces the transparent receiver to the
ENTER HUNT MODE
resets receive and transmit parameters.
Description
RESTART TRANSMIT
RESTART TRANSMIT
Description
SCC Transparent Mode
command is received.
is received.
28-7