149
Chapter 5
Memory Access Control Function
Preliminary User’s Manual U15839EE1V0UM00
5.2.4 Page ROM configuration register (PRC)
This register specifies whether page ROM on-page access is enabled or disabled. If on-page access is
enabled, the masking address (no comparison is made) out of the addresses (A3 to A6) corresponding
to the configuration of the page ROM being connected to and the number of bits that can be read con-
tinuously, as well as the number of waits corresponding to the internal system clock, are set.
This register can be read/written in 16-bit units.
Figure 5-5:
Page ROM Configuration Register (PRC)
Caution:
Write to the PRC register after reset, and then do not change the set value. Also, do
not access an external memory area other than that for this initialization routine until
initial setting of the PRC register is finished. However, it is possible to access exter-
nal memory areas whose initialization has been finished.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
PRC
0
PRW2 PRW1 PRW0
0
0
0
0
0
0
0
0
MA6
MA5
MA4
MA3 FFFFF49AH 7000H
Bit Position
Bit Name
Function
14 to 12
PRW2 to
PRW0
Page-ROM On-page Wait Control
Sets the number of waits corresponding to the internal system clock.
The number of waits set by this bit are inserted only when on-page. When off-page,
the waits set by registers DWC0 and DWC1 are inserted.
PRW2
PRW1
PRW0
Number of Inserted Wait Cycles
0
0
0
0
0
0
1
1
0
1
0
2
0
1
1
3
1
0
0
4
1
0
1
5
1
1
0
6
1
1
1
7
3 to 0
MA6 to
MA3
Mask Address
Each respective address (A6 to A3) corresponding to MA6 to MA3 is masked (masked
by 1). The masked address is not subject to comparison during on/off-page judgment.
It is set according to the number of continuously readable bits.
MA6
MA5
MA4
MA3
Number of Continuously Readable Bits
0
0
0
0
4 words × 16 bits (8 words × 8 bits)
0
0
0
1
8 words × 16 bits (16 words × 8 bits)
0
0
1
1
16 words × 16 bits (32 words × 8 bits)
0
1
1
1
32 words × 16 bits (64 words × 8 bits)
1
1
1
1
64 words × 16 bits (128 words × 8 bits)
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