Refresh Cycle Priority Order: When there are simultaneous bus requests, the priority order is:
(High)
External bus master > refresh controller > DMA controller > CPU
(Low)
For details see section 6.3.7, Bus Arbiter Operation.
Wait State Insertion: When bit AST3 is set to 1 in ASTCR, the wait state controller (WSC) can
insert wait states into bus cycles and refresh cycles. For details see section 6.3.5, Wait Modes.
Self-Refresh Mode: Some pseudo-static RAM devices have a self-refresh function. After the
SRFMD bit is set to 1 in RFSHCR, when a transition to software standby mode occurs, the
H8/3048 Series’ CS
3
output goes high and its
RFSH
output goes low so that the pseudo-static
RAM self-refresh function can be used. On exit from software standby mode, the
RFSH
output
goes high.
Table 7-8 shows the pin states in software standby mode. Figure 7-16 shows the signal output
timing.
Table 7-8 Pin States in Software Standby Mode (2) (PSRAME = 1, DRAME = 0)
Software Standby Mode
Signal
SRFMD = 0
SRFMD = 1 (Self-Refresh Mode)
CS
3
High
High
RD
High-impedance
High-impedance
HWR
High-impedance
High-impedance
LWR
High-impedance
High-impedance
RFSH
High
Low
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