r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 281

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

6.8.7
CAS latency is controlled by settings of the W22 to W20 bits of WTCRB. Set the CAS latency
count, as shown in table 6.11, by the setting of synchronous DRAM. Depending on the setting, the
CAS latency control cycle (T
AST2 bit of ASTCR. Figure 6.57 shows the CAS latency control timing when synchronous
DRAM of CAS latency 3 is connected.
The initial value of W22 to W20 is H'7. Set the register according to the CAS latency of
synchronous DRAM to be connected.
Table 6.11 Setting CAS Latency
W22
0
1
CAS Latency Control
W21
0
1
0
1
W20
0
1
0
1
0
1
0
1
c1
) is inserted. WTCRB can be set regardless of the setting of the
Description
Connect synchronous DRAM of CAS
latency 1
Connect synchronous DRAM of CAS
latency 2
Connect synchronous DRAM of CAS
latency 3
Connect synchronous DRAM of CAS
latency 4
Reserved (must not be used)
Reserved (must not be used)
Reserved (must not be used)
Reserved (must not be used)
Rev. 1.00 Sep. 19, 2008 Page 251 of 1342
Section 6 Bus Controller (BSC)
CAS Latency Control
Cycle Inserted
0 state
1 state
2 states
3 states
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REJ09B0467-0100