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SH7021 Datasheet(PDF) 154 Page - Renesas Technology Corp |
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SH7021 Datasheet(HTML) 154 Page - Renesas Technology Corp |
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154 / 509 page ![]() 136 RENESAS A23 A8 A7 A0 A21 A16 A15 A0 A23 A22 A21 A0 A21 A0 RAS = Low level Internal address Address pin CAS = Low level Internal address Address pin Undefined output Figure 8.16 Address Multiplexing States (8-bit shift) 8.5.2 Basic Timing There are two types of DRAM accesses: short pitch and long pitch. Short pitch or long pitch can be selected for the respective bus cycles using the RW1 and WW1 bits of WCR1 and the DRW1 and DWW1 bits of WCR2. When the corresponding bits are cleared to 0, DRAM access is short pitch and column address output occurs in 1 state. When these bits are 1, DRAM access is long pitch and column address output occurs in 2 states. Figure 8.17 shows short pitch timing; figure 8.18 shows long pitch timing. The high-level duty of the CAS signal can also be selected between 50% and 35% of the TC state when access is short pitch. By setting the CDTY bit to 1, high level duty becomes 35% and DRAM access time can be lengthened. Only set to 1 when the operating frequency is a minimum of 10 MHz. |
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