Ready Function - Fujitsu MB90480 Series Hardware Manual

7.5.2

Ready function

By setting the P56/RDY pin or defining the automatic ready function selection register
(ARSR), access to low-speed memory and peripheral circuits is enabled. If the RYE bit
in the bus control signal selection register (EPCR) is set to "1", wait cycles are
generated during the period where the "L" level is input to the P56/RDY pin while
access to the external area is in progress. Thus, the access cycle can be extended.
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Ready function
2
The F MC-16LX has two types of built-in auto-ready functions for external memory. The auto-
ready functions enable the access cycle to be extended by inserting 1 to 3 wait cycles
automatically without an external circuit when access occurs to the external area within the
following address ranges: a low-order address allocated between 002000
high-order address allocated between 800000
setting the LMR1 and LMR0 bits of ARSR (external area of a low-order address) and the HMR1
and HMR0 bits of ARSR (external area of a high-order address).
Furthermore, the F
independent of those for external memory. This function enables the access cycle to be
extended by inserting 1 to 3 wait cycles automatically without an external circuit when access
occurs to the external area between addresses 0000D0
by setting the IOR1 and IOR0 bits in ARSR.
With the auto-ready functions for either external memory or external I/O, if the RYE bit of EPCR
is set to "1" when the "L" level is input to the P56/RDY pin upon completion of the wait cycle
generated by auto-ready, the wait cycle continues as it is.
The timing charts of the ready function in the non-multiplex mode and multiplex mode are
shown below. In both modes, the top figure shows the case where the ready function is not set
and the bottom figure shows the case where the ready function is set.
Note:
If the AC rating is not satisfied for input from the RDY pin, be careful because this device may enter
the runaway state.
2
MC-16LX has built-in auto-ready function for external I/O that is
CHAPTER 7 MODE SETTING
and FFFFFF . These functions are evoked by
H H
and 0000FF
H H
and 7FFFFF , and a
H H
. This function is evoked
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