Bus Configuration Register (Bcr) - Motorola MPC8260 PowerQUICC II User Manual

Part II. ConÞguration and Reset
Bits 0 1 2
Field EBM APD
Reset Depends on reset conÞguration sequence. See Section 5.4.1, ÒHard Reset ConÞguration Word.Ó
R/W
Bits 16 17 18
Field NPQM
Reset Depends on reset conÞguration sequence. See Section 5.4.1, ÒHard Reset ConÞguration Word.Ó
R/W
Addr
Figure 4-21. Bus Configuration Register (BCR)
Table 4-9 describes BCR Þelds.
Bits Name
0 EBM External bus mode.
0 Single MPC8260 bus mode is assumed
1 60x-compatible bus mode. For more information refer to Section 8.2, ÒBus ConÞguration.Ó
1Ð3 APD Address phase delay. SpeciÞes the minimum number of address tenure wait states for address
operations initiated by a 60x bus master. BCR[APD] speciÞes the minimum number of address
tenure wait states for address operations initiated by 60x-bus devices. APD indicates how many
cycles the MPC8260 should wait for ARTRY, but because it is assumed that ARTRY can be
asserted (by other masters) only on cachable address spaces, APD is considered only on
transactions that hit one of the 60x-assigned memory controller banks and have the GBL signal
asserted during address phase.
4 L2C Secondary cache controller. See Chapter 11, ÒSecondary (L2) Cache Support.Ó
0 No secondary cache controller is assumed.
1 An external secondary cache controller is assumed.
5Ð7 L2D L2 cache hit delay. Controls the number of clock cycles from the assertion of TS until HIT is valid.
8 PLDP Pipeline maximum depth. See Section 8.4.5, ÒPipeline Control.Ó
1 The pipeline maximum depth is zero.
0 The pipeline maximum depth is one.
9 EAV Enable address visibility. Normally, when the MPC8260 is in single-MPC8260 bus mode, the bank
select signalsfor SDRAM accesses are multiplexed on the 60x bus address lines. So, for SDRAM
accesses, the internal address is not visible for debug purposes. However the bank select signals
can also be driven on dedicated pins (see SIUMCR[APPC]). In this case EAV can be used to force
address visibility.
0 Bank select signals are driven on 60x bus address lines. There is no full address visibility.
1 Bank select signals are not driven on address bus. During READ and WRITE commands to
SDRAM devices, the full address is driven on 60x bus address lines.
10Ð11 Ñ Reserved, should be cleared.
12 ETM Compatibility mode enable. See Section 8.4.3.8, ÒExtended Transfer Mode.Ó
0 Strict 60x bus mode. Extended transfer mode is disabled.
1 Extended transfer mode is enabled.
4-26
3 4 5 6
L2C L2D
19 20 21 22
Ñ EXDD
Table 4-9. BCR Field Descriptions
MPC8260 PowerQUICC II UserÕs Manual
7 8 9 10 11
PLDP EAV Ñ
R/W
23 24 25 26 27
Ñ ISPS
R/W
0x10024
Description
12 13 14 15
ETM LETM EPAR LEPAR
28 29 30 31
Ñ
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