UPD784938 Datasheet, PDF (628/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 24 LOCAL BUS INTERFACE FUNCTION
24.3 Pseudo-Static RAM Refresh Function
The µPD784938 incorporates a pseudo-static RAM refresh function for direct connection of pseudo-static RAM.
The pseudo-static RAM refresh function outputs refresh pulses at any desired intervals. The refresh pulse output interval
is specified by the refresh mode register (RFM) setting.
The refresh area specification register (RFA) specifies the addresses on which refresh operations can be performed at
the same time as memory access operations. This enables bus cycle insertions for refresh operations to be greatly
decreased, thus minimizing the reduction in performance due to refresh operations.
The µPD784938 is provided with a function for supporting self-refresh operations that offers low power consumption
by a pseudo-static RAM application system.
Cautions 1. The refresh function cannot be used when the bus hold function is used.
2. If the pseudo-static RAM refresh function is used when the address wait function is used, the
refresh pulse is output and, at the same time, the memory is accessed. Therefore, do not use the
pseudo-static RAM refresh function when using the address wait function.
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Preliminary User’s Manual U13987EJ1V0UM00