TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual
13-72
V2.0, 2007-07
EBU, V2.0
Figure 13-27 Possible BFCLKO Configurations
13.9.7
BFCLKI Input and Burst Flash Clock Feedback
The EBU Burst Mode control logic can be configured to use a clock feedback signal at
BFCLKI to maximize the operating frequency for a given Flash device. Clock feedback
functionality is enabled by setting EBU_BFCON.FDBKEN = 1.
When enabled, the first sampling stage for the read data is clocked by BFCLKI instead
of by BFCLKO. The data is then re-synchronized to BFCLKO internally before being
passed to the normal logic. When the clock feedback mode is used, BFCLKI can
therefore be skewed by almost an entire BFCLKO cycle relative to the internal LMBCLK
clock without losing data integrity.
A side effect of using clock feedback mode is an increase in data latency of 2 cycles of
BFCLKO. The value for this increased latency in LMBCLK clock cycles must be
programmed into bit field EBU_BFCON.DTALTNCY to ensure that data is sampled on
the correct clock edge.
LMBCLK
MCT05738_mod
BFCLKO
EXTCLOCK = 00
B
BFCLKO
EXTCLOCK = 01
B
BFCLKO
EXTCLOCK = 10
B
BFCLKO
EXTCLOCK = 11
B