Cypress Semiconductor FX2LP Technical Information Seite 426

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EZ-USB FX2 Technical Reference Manual
Page 15-106 EZ-USB FX2 Technical Reference Manual v2.1
The minimum delay length is a function of the IFCLK and CLKOUT (CPU Clock) frequencies, and
is determined by the equation:
The required delay length is smallest when the CPU is running at its slowest speed (12 MHz, 83.2
ns/cycle) and IFCLK is running at its fastest speed (48 MHz, 20.8 ns/cycle). Under those condi-
tions, the minimum required delay is:
The longest delay is required when the CPU is running at its fastest speed (48MHz, 20.8 ns/cycle)
and IFCLK is running much slower (e.g., 5.2 MHz, 192 ns/cycle):
The most-typical FX2 configuration, IFCLK and CLKOUT both running at 48 MHz, requires a mini-
mum delay of:
The Frameworks fimware supplied with the EZ-USB FX2 Development Kit includes a macro,
called SYNCDELAY, which implements the synchronization delay. The macro is in the file
fx2sdly.h.
Minimum Sync Delay, in CPU cycles 1.5
IFCLK Period
CLKOUT Period
-----------------------------------------
1+


×=
Note:
n means round n upward
1.5
20.8
83.2
----------
1+


× 1.5 1.25()× 1.875 2 CPU Cycles===
1.5
192
20.8
----------
1+


× 1.5 10.23()× 15.3 16 CPU Cycles===
1.5
20.8
20.8
----------
1+


× 1.5 2()× 3 3 CPU Cycles===
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