CHAPTER 6 BUS CONTROL
User’s Manual U14272EJ3V0UM
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6.4.2 Mixed memory mode (EDO DRAM only)
The MEMCFG_REG register provides two bits each for Bank 0 and Bank 1 to set types of DRAMs to be used.
This allows the two banks to be configured with different types of DRAMs, for example, Bank 0 can be mapped on 64
Mbit devices and Bank 1 on 16 Mbit devices, to optimize the cost of the total memory required.
Table 6-2. V
R
4181 EDO DRAM Capacity
Bank 0
Bank 1
Total DRAM capacity
16 Mbits
0
2 MB
16 Mbits
16 Mbits
4 MB
64 Mbits
0
8 MB
16 Mbits
64 Mbits
10 MB
64 Mbits
16 Mbits
10 MB
64 Mbits
64 Mbits
16 MB
6.4.3 EDO DRAM timing parameters
The following table shows examples of EDO DRAM timing parameters when using EDO DRAMs with access time
of 60 ns. These parameters are set in EDOMCYTREG register.
TClock
frequency
RAS to CAS
delay
CAS pulse
width
CAS precharge
RAS precharge
RAS pulse
width
Self refresh
RAS precharge
66 MHz
3 TClock
1 TClock
1 TClock
3 TClock
3 TClock
8 TClock
50 MHz
2 TClock
1 TClock
1 TClock
2 TClock
3 TClock
6 TClock
33 MHz
2 TClock
1/2 TClock
1/2 TClock
2 TClock
2 TClock
4 TClock
25 MHz
2 TClock
1/2 TClock
1/2 TClock
1 TClock
2 TClock
3 TClock