User manual

I
2
C Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 39-11
39.6 I
2
C Commands
The I
2
C transmit and receive commands, shown in Table 39-8, are issued to the CP command register
(CPCR).
39.7 The I
2
C Buffer Descriptor (BD) Table
As shown in Figure 39-12, buffer descriptors (BDs) are organized into separate RxBD and TxBD tables
in dual-port RAM. The tables have the same basic configuration as for the SCCs and SMCs and form
circular queues that determine the order buffers are transferred. The CP uses BDs to confirm reception and
transmission or to indicate error conditions so that the core knows buffers have been serviced. The buffers
themselves can be placed in external memory or in any unused parameter area of the dual-port RAM.
3–4 BO Byte ordering. Selects the required byte ordering for the buffer. If BO is changed on-the-fly, it takes
effect at the beginning of the next frame or BD.
00 True little-endian. Note this mode can only be used with 32-bit port size memory.
01 Big-endian
1x Munged little-endian
5 TC2 Transfer code 2. Contains the transfer code value of TC[2], used during this SDMA channel memory
access. TC[0–1] is driven with a 0b11 to identify this SDMA channel access as a DMA-type access.
6 DTB Data bus indicator.
0 Use 60x bus for SDMA operation.
1 Use local bus for SDMA operation.
7 — Reserved, should be cleared.
Table 39-8. 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.
Table 39-7. RFCR/TFCR Field Descriptions
Bits Name Description