CHAPTER 5 MEMORY ACCESS CONTROL FUNCTION
User’s Manual U12688EJ4V0UM00
134
5.2.4 Page ROM configuration register (PRC)
This specifies whether page ROM on-page access is enabled or disabled. Also, if on-page access is enabled, the
masked addresses (no comparison is made) out of the addresses (A3 to A5) corresponding to the configuration of the
connected page ROM and the number of bits that can be read continuously, as well as the number of waits
corresponding to the internal system clock, are set.
This register can be read/written in 8- or 1-bit units.
0
MA3
Address
FFFFF224H
After reset
70H
1
MA4
2
MA5
3
0
4
PRW0
5
PRW1
6
PRW2
7
PAE
PRC
Bit Position
Bit Name
Function
7
PAE
Page ROM On-page Access Enable
Specifies whether page ROM on-page access is enabled or disabled.
0: Disable
1: Enable
Page-ROM On-page Access Wait Control
Sets the number of waits corresponding to the internal system clock.
The waits set by this bit are inserted only for on-page access. For off-page access, the
waits set by registers DWC1 and DWC2 are inserted (refer to 4.6 Wait Function).
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
6 to 4
PRW2 to
PRW0
Mask Address
Each address (A5 to A3) corresponding to MA5 to MA3 is 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.
MA5
MA4
MA3
Number of Continuously Readable Bits
0
0
0
4 words
×
16 bits (8 words
×
8 bits)
0
0
1
8 words
×
16 bits (16 words
×
8 bits)
0
1
1
16 words
×
16 bits (32 words
×
8 bits)
1
1
1
32 words
×
16 bits (64 words
×
8 bits)
2 to 0
MA5 to
MA3
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 the one for this initialization routine until the initial setting
of the PRC register is complete. However, it is possible to access an external memory area
whose initialization is complete.
Содержание V850E/MS1 UPD703100
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