147
Chapter 5
Memory Access Control Function
Preliminary User’s Manual U15839EE1V0UM00
5.2.3 On-page/off-page
judgment
Whether a page ROM cycle is on-page or off-page is judged by latching the address of the previous
cycle and comparing it with the address of the current cycle.
Through the page ROM configuration register (PRC), according to the configuration of the connected
page ROM and the number of continuously readable bits, one of the addresses (A3 to A6) is set as the
masking address (no comparison is made).
Figure 5-4:
On-Page/Off-Page Judgment during Page ROM Connection (1/2)
(a) In case of 16-Mbit (1 M × 16 bits) page ROM (4-word page access)
(b) In case of 16-Mbit (1 M × 16 bits) page ROM (8-word page access)
a23
a22
a21
a20
a7
a6
a5
a4
a3
A23
A22
A21
A20
A7
A6
A5
A4
A3
A2
A1
A1
A0
A0
Internal address latch
(immediately preceding
address)
V850E/CA2
address output
Page ROM address
A19
Off-page address
On-page address
A6
A5
A4
A3
A2
MA6
0
MA5
0
MA4
0
MA3
0
PRC register setting
Comparison
Continuous reading possible:
16-bit data bus width
×
4 words
a23
a22
a21
a20
a7
a6
a5
a4
a3
A23
A22
A21
A20
A7
A6
A5
A4
A3
A2
A1
A1
A0
A0
Internal address latch
(immediately preceding
address)
V850E/CA2
address output
Page ROM address
A19
Off-page address
On-page address
Continuous reading possible:
16-bit data bus width
×
8 words
A6
A5
A4
A3
A2
MA6
0
MA5
0
MA4
0
MA3
1
PRC register setting
Comparison
Summary of Contents for mPD703128
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