Motorola PowerQUICC II MPC8280 Series Reference Manual page 1375

Table 39-8. SPI RxBD Status and Control Field Descriptions (continued)
Bits Name
14 OV Overrun. Set when a receiver overrun occurs during reception (slave mode only). The SPI updates
OV after the received data is placed in the buffer.
15 ME Multimaster error. Set when this buffer is closed because SPISEL was asserted when the SPI was
in master mode. Indicates a synchronization problem between multiple masters on the SPI bus. The
SPI updates ME after the received data is placed in the buffer.
39.7.1.2 SPI Transmit BD (TxBD)
Data to be sent with the SPI is sent to the CP by arranging it in buffers referenced by TxBDs
in the TxBD table. TxBD fields should be prepared before data is sent. The format of an
TxBD is shown in Figure 39-12.
0 1 2
Offset + 0 R — W
Offset + 2
Offset + 4
Offset + 6
Table 39-9 describes the TxBD status and control fields.
Table 39-9. SPI TxBD Status and Control Field Descriptions
Bits Name
0 R Ready.
0 The buffer is not ready to be sent. This BD or its buffer can be modified. The CP clears R (unless
RxBD[CM] is set) after the buffer is sent (unless RxBD[CM] is set) or an error occurs.
1 The buffer is ready for transmission or is being sent. The BD cannot be modified once R is set.
1 — Reserved, should be cleared.
2 W Wrap (last BD in TxBD 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 using the BD pointed
to by TBASE (top of the table). The number of BDs in this table is determined only by the W bit
and overall space constraints of the dual-port RAM.
3 I Interrupt.
0 No interrupt is generated after this buffer is processed; SPIE[TXE] is unaffected.
1 SPIE[TXB] or SPIE[TXE] are set when this buffer is processed and causes interrupts if not
masked.
4 L Last.
0 This buffer does not contain the last character of the message.
1 This buffer contains the last character of the message.
5 — Reserved, should be cleared.
MOTOROLA
Freescale Semiconductor, Inc.
3 4 5 6
I L — CM
Data Length
Tx Buffer Pointer
Figure 39-12. SPI TxBD
Chapter 39. Serial Peripheral Interface (SPI)
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The SPI Buffer Descriptor (BD) Table
Description
7 8 9 10 11
—
Description
12 13 14 15
UN ME
39-17