MOTOROLA
Chapter 32. I2C Controller
32-11
Part V. The Communications Processor Module
Table 32-7 describes the RFCR/TFCR bit Þelds.
32.6 I
2
C Commands
The I
2
C transmit and receive commands, shown in Table 32-8, are issued to the CPM
command register (CPCR).
32.7 I
2
C Buffer Descriptor (BD) Tables
As shown in Figure 32-12, buffer descriptors (BDs) are organized into separate Rx and
TxBD tables in dual-port RAM. The tables have the same basic conÞguration as for the
SCCs and SMCs and form circular queues that determine the order buffers are transferred.
The CPM uses BDs to conÞrm reception and transmission or to indicate error conditions so
Bit
0
1
2
3
4
5
6
7
Field
Ñ
BO
AT[1Ð3]
Reset
0000_0000
R/W
R/W
Addr
I2C Base + 04 (RFCR)/I2C Base + 05 (TFCR)
Figure 32-11. I
2
C Function Code Registers (RFCR/TFCR)
Table 32-7. RFCR/TFCR Field Descriptions
Bits
Name
Description
0Ð2
Ñ
Reserved, should be cleared.
3Ð4
BO
Byte ordering. Set BO to select the required byte ordering for the buffer. If BO is changed on-the-ßy, it
takes effect at the beginning of the next frame (Ethernet, HDLC, and transparent) or at the beginning
of the next BD. See Appendix A, ÒByte Ordering.Ó
00 Reserved
01 PowerPC little-endian.
1x Big-endian or true little-endian.
5Ð7
AT[1Ð3]
Address type 1Ð3. Contains the user-deÞned function code value used during the SDMA channel
memory access. AT0 is always driven high to identify this channel access as a DMA-type access.
Table 32-8. I
2
C Transmit/Receive Commands
Command
Description
INIT
TX
PARAMETERS
Initializes all transmit parameters in the parameter RAM to their reset state. Should be issued only
when the transmitter is disabled. The
INIT
TX
AND
RX
PARAMETERS
command can also be used to reset
both the Tx and Rx parameters.
CLOSE
RXBD
Forces the I
2
C controller to close the current Rx BD and use the next BD for subsequently received
data. If the controller is not receiving data, no action is taken. Use this command to extract data from a
partially full buffer.
INIT
RX
PARAMETERS
Initializes all receive parameters in the parameter RAM to their reset state. Should be issued only when
the receiver is disabled. The
INIT
TX
AND
RX
PARAMETERS
command can also be used to reset both the
Tx and Rx parameters.
Содержание MPC860 PowerQUICC
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