CHAPTER 5 MEMORY ACCESS CONTROL FUNCTION
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User’s Manual U14359EJ4V0UM
5.3.3 Address multiplex function
Depending on the value of the DAW0n and DAW1n bits in DRAM configuration register n (SCRn), the row address
and column address outputs in the DRAM cycle are multiplexed as shown in Figure 5-7 (n = 1, 3, 4, 6). In Figure 5-7,
a0 to a25 show the addresses output from the CPU and A0 to A25 show the address pins of the V850E/MA1.
For example, when DAW1n and DAW0n = 11, it indicates that a12 to a22 are output as row addresses and a1 to
a11 are output as column addresses from the address pins (A1 to A11).
Figure 5-7. Row Address/Column Address Output
A15
a15
A14
a25
A13
a24
A25 to A18
Address pin
a25 to a18
Row address
(DAW1n, DAW0n = 11)
A17
a17
A16
a16
A12
a23
A11
a22
A10
a21
A9
a20
A8
a19
A7
a18
A6
a17
A5
a16
A4
a15
A3
a14
A2
a13
A1
a12
A0
a11
a25 a24 a23
a25 to a18
Row address
(DAW1n, DAW0n = 10)
a17 a16
a22 a21 a20 a19 a18 a17 a16 a15 a14 a13 a12 a11 a10
a24 a23 a22
a25 to a18
Row address
(DAW1n, DAW0n = 01)
a17 a25
a21 a20 a19 a18 a17 a16 a15 a14 a13 a12 a11 a10 a9
a23 a22 a21
a25 to a18
Row address
(DAW1n, DAW0n = 00)
a25 a24
a20 a19 a18 a17 a16 a15 a14 a13 a12 a11 a10
a9
a8
a15 a14 a13
a25 to a18
Column address
a17 a16
a12 a11 a10
a9
a8
a7
a6
a5
a4
a3
a2
a1
a0
Remark
n = 1, 3, 4, 6
Table 5-1 shows the relationship between the DRAM that can be connected and the address multiplex width. The
DRAM space differs according to the DRAM that is connected, as shown in Table 5-1.
Table 5-1. Example of DRAM and Address Multiplex Width
DRAM Capacity (Bits) and Configuration
Address Multiplex Width
256 K
1 M
4 M
16 M
64 M
DRAM Space
Note
(Bytes)
8 bits (DAW1n, DAW0n = 00)
64 K
×
4
−
−
−
−
128 K
−
256 K
×
4
256 K
×
16
−
−
512 K
−
−
512 K
×
8
−
−
1 M
9 bits (DAW1n, DAW0n = 01)
−
−
−
−
4 M
×
16
8 M
−
−
1 M
×
4
1 M
×
16
−
2 M
−
−
−
2 M
×
8
−
4 M
10 bits (DAW1n, DAW0n = 10)
−
−
−
−
4 M
×
16
8 M
11 bits (DAW1n, DAW0n = 11)
−
−
−
4 M
×
4
−
8 M
Note
When the data bus width is 16 bits
Remark
n = 1, 3, 4, 6