MOTOROLA Chapter 34. I2C Controller 34-9
Part IV. Communications Processor Module

Table 34-5 describes I2COM Þelds.

34.5 I2C Parameter RAM

The I2C controller parameter table is used for the general I2C parameters and is similar to

the SCC general-purpose parameter RAM. The CP accesses the I2C parameter table using

a user-programmed pointer (I2C_BASE) located in the parameter RAM; see

Section 13.5.2, ÒParameter RAM.Ó The I2C parameter table can be placed at any 64-byte

aligned address in the dual-port RAMÕs general-purpose area (banks #1Ð#8). The user must

initialize certain parameter RAM values before the I2C is enabled; the CP initializes the

other values. Software usually does not access parameter RAM entries once they are

initialized; they should be changed only when the I2C is inactive.

Bit 0 1 2 3 4 5 6 7
Field STR Ñ M/S
Reset 0000_0000
R/W R/W
Addr 0x1186C

Figure 34-10. I2C Command Register (I2COM)

Table 34-5. I2COM Field Descriptions

Bits Name Description
0 STR Start transmit. In master mode, setting STR causes the I2C controller to start sending data from the
I2C Tx buffers if they are ready. In slave mode, setting STR when the I2C controller is idle causes it to
load the Tx data register from the I2C Tx buffer and start sending when it receives an address byte that
matches the slave address with R/W = 1. STR is always read as a 0.
1Ð6 Ñ Reserved and should be cleared.
7 M/S Master/slave. ConÞgures the I2C controller to operate as a master or a slave.
0I
2C is a slave.
1I
2C is a master.

Table 34-6. I2C Parameter RAM Memory Map

Offset 1Name Width Description
0x00 RBASE Hword Rx/TxBD table base address. Indicate where the BD tables begin in the dual-port RAM.
Setting Rx/TxBD[W] in the last BD in each BD table determines how many BDs are
allocated for the Tx and Rx sections of the I2C. Initialize RBASE/TBASE before enabling
the I2C. Furthermore, do not conÞgure BD tables of the I2C to overlap any other active
controllerÕs parameter RAM.
RBASE and TBASE should be divisible by eight.
0x02 TBASE Hword
0x04 RFCR Byte Rx/Tx function code registers. The function code registers contain the transaction
speciÞcation associated with SDMA channel accesses to external memory. See
Figure 34-11 and Table 34-7.
0x05 TFCR Byte