MOTOROLA
Chapter 8. The 60x Bus
8-13
Part III. The Hardware Interface
8.4.3.2 Transfer Code Signals TC[0Ð2]
The transfer code signals, TC[0Ð2], provide supplemental information about the
corresponding address (mainly regarding the source of the transaction). Note that TC
x
signals can be used with the TT[0Ð4] and TBST to further deÞne the current transaction.
8.4.3.3 TBST and TSIZ[0Ð3] Signals and Size of Transfer
As shown in Table 8-4, the transfer size signals (TSIZ[0Ð3]) and the transfer burst signal
(TBST) together indicate the size of the requested data transfer. These signals can be used
with address bits A[27Ð31] and the device port size to determine which portion of the data
bus contains valid data for a write transaction or which portion of the bus should contain
valid data for a read transaction.
The MPC8260 uses four double-word burst transactions for transferring cache blocks. For
these transactions, TSIZ[0Ð3] are encoded as 0b0010, and address bits A[27Ð28] determine
which double-word is sent Þrst.
The MPC8260 supports critical-word-Þrst burst transactions (double-word-aligned) from
the processor. The MPC8260 transfers the critical double word of data Þrst, followed by the
double words from increasing addresses, wrapping back to the beginning of the eight-word
block as required.
Table 8-3 Transfer Code Encoding
TC[0Ð2]
Read Write
000
Core data transaction
Any write
001
Core touch load
Ñ
010
Core instruction fetch
Ñ
011
Reserved
Ñ
100
Reserved
101
Reserved
110
DMA function code 0
111
DMA function code 1
Table 8-4. Transfer Size Signal Encoding
TBST
TSIZ[0Ð3]
Transfer Size
Comments
Source
Negated
0 0 0 1
1 Byte
Byte
Core and DMA
Negated
0 0 1 0
2 Bytes
Half-word
Core and DMA
Negated
0 0 1 1
3 Bytes
Ñ
Core and DMA
Negated
0 1 0 0
4 Bytes
Word
Core and DMA
Negated
0 1 0 1
5 Bytes
Extended 5 bytes
SDMA (MPC8260 only)
Negated
0 1 1 0
6 Bytes
Extended 6 bytes
SDMA (MPC8260 only)
Содержание MPC8260 PowerQUICC II
Страница 1: ...MPC8260UM D 4 1999 Rev 0 MPC8260 PowerQUICC II UserÕs Manual ª ª ...
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Страница 88: ...1 18 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA Part I Overview ...
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Страница 430: ...Part IV viii MOTOROLA Part IV Communications Processor Module ...
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Страница 1002: ...Index 22 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA INDEX ...
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