MPC8280 datasheet(881/1386 Pages) FREESCALE

881 / 1386 page

Serial Management Controllers (SMCs)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

28-27

Data length and buffer pointer fields are described in Section 20.2, “SCC Buffer Descriptors (BDs).”

28.4.9

SMC Transparent TxBD

Data is sent to the CP for transmission on an SMC channel by arranging it in buffers referenced by the

channel TxBD table. The CP uses BDs to confirm transmission or indicate error conditions so the

processor knows buffers have been serviced.

Table 28-15 describes SMC transparent TxBD fields.

123

456

789

Offset + 0

—

—UN

—

Offset + 2

Data Length

Offset + 4

Tx Data Buffer Pointer

Offset + 6

Table 28-14. SMC Transparent TxBD

Table 28-15. SMC Transparent TxBD Field Descriptions

Bits Name

Description

Ready.

0 The buffer is not ready for transmission. The BD and buffer can be updated. The CP clears R after the buffer

is sent or after an error occurs.

1 The user-prepared data buffer is not sent or is being sent. BD fields cannot be updated if R is set.

—

Reserved, should be cleared.

Wrap (final BD in table).

0 Not the last BD in the table.

1 Last BD in the table. After this buffer is used, the CP receives incoming data into the first BD that TBASE

points to. The number of TxBDs in this table is programmable and determined by theW bit and overall space

constraints of the dual-port RAM.

Interrupt.

0 No interrupt is generated after this buffer is serviced; SMCE[TXE] is unaffected.

1 SMCE[TXB] or SMCE[TXE] are set when the buffer is serviced. They can cause interrupts if they are enabled.

Last in message.

0 The last byte in the buffer is not the last byte in the transmitted transparent frame. Data from the next transmit

buffer (if ready) is sent immediately after the last byte of this buffer.

1 The last byte in this buffer is the last byte in the transmitted transparent frame. After this buffer is sent, the

transmitter requires synchronization before the next buffer is sent.

—

Reserved, should be cleared.

Continuous mode.

0 Normal operation.

1 The CP does not clear R after this BD is closed, allowing the buffer to be automatically resent when the CP

accesses this BD again. However, the R bit is cleared if an error occurs during transmission, regardless of

how CM is set.

7–13

—

Reserved, should be cleared.

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