34-10
MPC8260 PowerQUICC II UserÕs Manual
MOTOROLA
Part IV. Communications Processor Module
0x06
MRBLR
Hword Maximum receive buffer length. DeÞnes the maximum number of bytes the MPC8260
writes to a Rx buffer before moving to the next buffer. The MPC8260 writes fewer bytes
to the buffer than the MRBLR value if an error or end-of-frame occurs. Buffers should not
be smaller than MRBLR.
Tx buffers are unaffected by MRBLR and can vary in length; the number of bytes to be
sent is speciÞed in TxBD[Data Length].
MRBLR is not intended to be changed while the I
2
C is operating. However it can be
changed in a single bus cycle with one 16-bit move (not two 8-bit bus cycles back-to-
back). The change takes effect when the CP moves control to the next RxBD. To
guarantee the exact RxBD on which the change occurs, change MRBLR only while the
I
2
C receiver is disabled. MRBLR should be greater than zero; it should be an even
number if the character length of the data exceeds 8 bits.
0x08
RSTATE
Word
Rx internal state.
2
Reserved for CP use.
0x0C
RPTR
Word
Rx internal data pointer
2
is updated by the SDMA channels to show the next address in
the buffer to be accessed.
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 modiÞed
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 modiÞed 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.
1
From the pointer value programmed in I2C_BASE at IMMR + 0x8AFC.
2
Normally, these parameters need not be accessed.
Table 34-6. I
2
C Parameter RAM Memory Map (Continued)
Offset
1
Name
Width
Description
Summary of Contents for MPC8260 PowerQUICC II
Page 1: ...MPC8260UM D 4 1999 Rev 0 MPC8260 PowerQUICC II UserÕs Manual ª ª ...
Page 66: ...lxvi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA ...
Page 88: ...1 18 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 120: ...2 32 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
Page 138: ...Part II iv MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II Configuration and Reset ...
Page 184: ...4 46 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part II ConÞguration and Reset ...
Page 202: ...Part III vi MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 266: ...8 34 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 382: ...10 106 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 392: ...11 10 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part III The Hardware Interface ...
Page 430: ...Part IV viii MOTOROLA Part IV Communications Processor Module ...
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Page 980: ...A 4 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Appendixes ...
Page 1002: ...Index 22 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA INDEX ...
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