Full-Handshaking And Ready Pin Usage In Asynchronous Write Mode - Texas Instruments OMAP5912 Reference Manual

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Full-Handshaking and Ready Pin Usage in Asynchronous Write Mode

50 OMAP3.2 Subsystem
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In full-handshaking mode, FLASH.RDY is monitored by the EMIFS to
control read access time. The access is completed when both internal wait
state WELEN expires and FLASH.RDY (ball V2) is asserted by the
external device. Full-handshaking is the default mode in both multiplexed
and non-multiplexed modes.
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ADV pulse width time and WE assertion time are not dependent on the
FLASH.RDY state.
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When FLASH.RDY is used to extend the access time, the access
completion is not controlled by internal delay generation. The CS and data
hold time setup from WE high is still fixed to one REF_CLK (Q cycle in
previous figures).
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Because FLASH.RDY is an asynchronous signal, a nonready device must
drive FLASH.RDY low enough time ahead of the minimum access time
completion. Depending on FLASH.RDY assertion low delay from CS
active and depending on REF_CLK frequency, a minimum WRWST value
could be needed for the FLASH.RDY state to be correctly monitored by
the EMIFS.
J
As an example, a minimum of WRWST=1 is needed for a nonready
device that drives ready low with 0 time delay from CS low, for a CS
configuration FCLKDIV=0.
SPRU749A