SH7020 Datasheet, PDF (154/509 Pages) Renesas Technology Corp – SuperH™ RISC engine

RAS = Low level
Internal address _A23
A8 A7
A0
Address pin
A21 A16 A15
A0
CAS = Low level
Undefined output
Internal address ^{A23 A22 A21}
A0
Address pin
A21
A0
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 T_C 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.
136 RENESAS