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Appendix B Rabbit 5000 Errata
401
A
PPENDIX
B. R
ABBIT
5000 E
RRATA
The Rabbit 5000 began shipping in 2008 on multiple platforms. Several bugs were found
in the design after the chip was released, and are discussed in this appendix.
B.1 Errata
The following bugs have been identified in the Rabbit 5000 design, and are present in all
devices currently available. All Dynamic C libraries have been corrected these issues, and
the compiler correctly generates operational code from C programs as noted below. How-
ever, customers should be aware of them when writing code in assembly.
1.
Noise in 802.11b Wi-Fi transmissions
— The state machine for 802.11b transmissions
can generate extra noise outside the allowed 802.11b frequency range in some situa-
tions. To avoid this possibility, the following corrections are implemented in the
Dynamic C Wi-Fi library:
(a) For 1 and 2 Mbps transmission rates, the noise only exists for certain clock
alignments with respect to other clocks in the design. When Wi-Fi is enabled,
the Wi-Fi clock is checked for proper alignment and restarted repeatedly until
the correct alignment occurs.
(b) For 5.5 and 11 Mbps, the noise will not exist for packet lengths that are multi-
ples of 11, again due to clock alignment. The Dynamic C Wi-Fi library will
pad all outgoing packets to a safe length to avoid the noise issue. Note that this
means that the maximum MTU is actually 1441 bytes and not the standard
1450.
2.
Instruction alignment issues
— there are several issues with alignment of particular
instructions in 16-bit mode; all instructions function properly in 8-bit mode. Dynamic
C will automatically align all instructions appropriately by adding NOP instructions to
the generated code. The instructions of concern in 16-bit mode and the required align-
ment are:
(a) LD pd,ps+d must be even-aligned.
(b) LD BCDE,d must be odd-aligned.
(c) LD HL,(n) must be even-aligned.
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