I2C Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 39-11
39.6 I2C Commands

The I2C transmit and receive commands, shown in Table 39-8, are issued to the CP command register

(CPCR).

39.7 The I2C Buffer Descriptor (BD) Table

As shown in Figure39- 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
5TC2 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.
6DTB Data bus indicator.
0 Use 60x bus for SDMA operation.
1 Use local bus for SDMA operation.
7 Reserved, should be cleared.

Table39-8. I2C 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 I2C controller to close the current RxBD 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.

Table39-7. RFCR/TFCR Field Descriptions

Bits Name Description