370
µ
PD78214 Sub-Series
(2) Self-refresh
Self-refresh is performed to retain the contents of pseudo static RAM when in standby mode.
(a) Setting self-refresh mode
When bit 4 (RFEN) of the RFM register is set to 1, and bit 7 (RFLV) is set to 0, pin REFRQ outputs a low-level
signal, requesting pseudo static RAM to enter self-refresh mode.
(b) Restoration from self-refresh
Refresh pulse output to pseudo static RAM is disabled for approximately 200 nsNote after the output level
of pin REFRQ goes high. The
µ
PD78214 drives pin REFRQ high, synchronized with the refresh timing
counter, so that refresh pulses are not output during a refresh disabled period.
To detect pin REFRQ going high, the read out level of bit RFLV is set to 1 when pin REFRQ goes high.
NoteThis time varies with the speed of the pseudo static RAM.
Fig. 13-21 Restoration Timing from Self-Refresh
Approx. 200 ns min.Note
REFRQ
Execution of set manipulation by software
Self-refresh mode
Output of
refresh timing counter
RFLV bit
NoteRefresh disabled period