Z8018x
Family MPU User Manual
88
UM005004-0918
Refresh Control Register (RCR)
The RCR specifies the interval and length of refresh cycles, while
enabling or disabling the refresh function.
Refresh Control Register (RCR: 36H)
Bit
7
6
5
4
3
2
1
0
Bit/Field
REFE
REFW
?
CYC1
CYC0
R/W
R/W
R/W
?
R/W
R/W
Reset
1
1
?
0
0
Note: R = Read W = Write X = Indeterminate ? = Not Applicable
Bit
Position Bit/Field R/W
Value
Description
7
REFE
R/W
0
1
REFE: Refresh Enable
Disables the refresh controller
Enables refresh cycle insertion.
6
REFW
R/W
0
1
Refresh Wait
(bit 6)
Causes the refresh cycle to be two clocks in duration.
Causes the refresh cycle to be three clocks in duration by
adding a refresh wait cycle (TRW).
1
–
0
CYC1
–
0 R/W
Cycle Interval
— CYC1 and CYC0 specify the interval
(in clock cycles) between refresh cycles. In the case of
dynamic RAMs requiring 128 refresh cycles every 2 ms
(or 256 cycles in every 4 ms), the required refresh interval
is less than or equal to 15.625
μ
s. Thus, the underlined
values indicate the best refresh interval depending on
CPU clock frequency. CYC0 and CYC1 are cleared to 0
during RESET. Refer to Table 11.
Содержание Z8018 Series
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