Infineon Technologies TC1784, User Manual

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TC1784
LMB External Bus Unit
User´s Manual 12-17 V1.1, 2011-05
EBUT13L-A, V1.16
12.7.4 Address Comparison
Standard Address Comparison Mode
When an Addressing Override Mode is not active, each of the four EBU regions can be
programmed for independent base addresses and lengths by bits and bit fields in
registers EBU_ADDRSELx.
•
Bit REGEN is the enable control of a region. If the region is disabled (REGEN = 0),
no address comparison will take place for the region.
• Bit field BASE specifies address bits A[31:12] of region x, where A[31:28] must only
point to segments 8, 10, 13, and 14 (see
Table 12-7 on Page 12-11 ).
1)
• Bit field MASK determines the length of a region. It specifies how many bits of a LMB
address must match the contents of the BASE(x) bit field (to a maximum of 15,
starting with A[26]). Note that address bits A[31:27] must always match.
• Bit WPROT write protects a region. If the region is protected (WPROT = 1), no
address comparison will take place for that region on a write access
2)
• Bit field ALTSEG determines the number of an alternate segment that can be used
for address comparison with A[31:28] (if enabled by ALTENAB = 1).
• Bit ALTENAB determines whether an additional alternate segment number as
defined by ALTSEG is used for address comparison.
The address comparison scheme is shown in Figure 12-4 .
1) There is no hardware lockout preventing other values being written to A[31:28], but in most cases this will
result in an inaccessible memory. Enabling a memory region at segment F8
H
will result in the memory region
conflicting with the registers. The EBU will not work correctly if this is done.
2) The WPROT bit also appiles to the read phase of a read modify write, LMB transaction. This is to prevent two
possible error conditions. The first would be where the read phase was accepted and the write phase errored.
This is an LMB protocol violation. The second would be where the read and write accesses occurred to
different memory addresses (if the read took place to a write protected region and there was an unprotected,
lower priority, region mapped to the same address space).