Freescale Semiconductor MPC8260 - Manual (Page 839)

Serial Management Controllers (SMCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 27-27
Data length and buffer pointer fields are described in Section 20.2, “SCC Buffer Descriptors (BDs).”
27.4.9 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 27-15 describes SMC transparent TxBD fields.
3 I Interrupt.
0 No interrupt is generated after this buffer is filled.
1 SMCE[RXB] is set when the CP completely fills this buffer indicating that the core must process
the buffer. The RXB bit can cause an interrupt if it is enabled.
4–5 — Reserved, should be cleared.
6 CM Continuous mode.
0 Normal operation.
1 The CP does not clear E after this BD is closed, allowing the buffer to be overwritten when the
CP next accesses this BD. However, E is cleared if an error occurs during reception, regardless
of how CM is set.
7–13 — Reserved, should be cleared.
14 OV Overrun. Set when a receiver overrun occurs during reception. The CP writes OV after the received
data is placed into the buffer.
15 — Reserved, should be cleared.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Offset + 0 R — W I L — CM — UN —
Offset + 2 Data Length
Offset + 4 Tx Data Buffer Pointer
Offset + 6
Table 27-14. SMC Transparent TxBD
Table 27-15. SMC Transparent TxBD Field Descriptions
Bits Name Description
0 R 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.
1 — Reserved, should be cleared.
Table 27-13. SMC Transparent RxBD Field Descriptions (continued)
Bits Name Description