I
2
C Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
39-10
Freescale Semiconductor
Figure 39-11
shows the RFCR/TFCR bit fields.
Table 39-7
describes the RFCR/TFCR bit fields.
0x10
RBPTR
Hword RxBD pointer. Points to the next descriptor the receiver transfers data to when it is in
an idle state or to the current descriptor during frame processing for each I
2
C channel.
After a reset or when the end of the descriptor table is reached, the CP initializes
RBPTR to the value in RBASE. Most applications should not write RBPTR, but it can
be modified when the receiver is disabled or when no receive buffer is used.
0x12
RCOUNT
Hword Rx internal byte count
2
is a down-count value that is initialized with the MRBLR value
and decremented with every byte the SDMA channels write.
0x14
RTEMP
Word
Rx temp.
2
Reserved for CP use.
0x18
TSTATE
Word
Tx internal state.
2
Reserved for CP use.
0x1C
TPTR
Word
Tx internal data pointer
2
is updated by the SDMA channels to show the next address
in the buffer to be accessed.
0x20
TBPTR
Hword TxBD pointer. Points to the next descriptor that the transmitter transfers data from when
it is in an idle state or to the current descriptor during frame transmission. After a reset
or when the end of the descriptor table is reached, the CP initializes TBPTR to the value
in TBASE.Most applications should not write TBPTR, but it can be modified when the
transmitter is disabled or when no transmit buffer is used.
0x22
TCOUNT
Hword Tx internal byte count
2
is a down-count value initialized with TxBD[Data Length] and
decremented with every byte read by the SDMA channels.
0x24
TTEMP
Word
Tx temp.
2
Reserved for CP use.
0x34
SDMATMP
Word
SDMA temp.
2
Reserved for CP use.
1
From the pointer value programmed in I2C_BASE at IMMR + 0x8AFC.
2
Normally, these parameters need not be accessed.
0
1
2
3
4
5
6
7
Field
GBL
BO
TC2
DTB
—
Reset
0000_0000
R/W
R/W
Addr
I2 04 (RFCR)/I2 05 (TFCR)
Figure 39-11. I
2
C Function Code Registers (RFCR/TFCR)
Table 39-7. RFCR/TFCR Field Descriptions
Bits
Name
Description
0–1
—
Reserved, should be cleared.
2
GBL
Global access bit
0 Disable memory snooping
0 Enable memory snooping
Table 39-6. I
2
C Parameter RAM Memory Map (continued)
Offset
1
Name
Width
Description
Summary of Contents for MPC8250
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