7733 datasheet(417/940 Pages) RENESAS

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APPLICATIONS

7733 Group User’s Manual

17–10

(3) Precautions on memory expansion

When specifications of the 7733 Group do not match those of an external memory as described in the

following to , some considerations about the circuit are necessary:

When using an external memory which requires a long address access time (ta(AD))

When using an external memory which outputs data within an interval of tpxz(E-DZ) after signal E’s

falling edge.

When using an external memory which outputs data for more than an interval of tpzx(E-DZ) after

signal E’s rising edge

When using an external memory which requires a long address access time (ta(AD))

When an external memory requires a long address access time (ta(AD)) which does not satisfy the 7733

Group’s tsu(D-E), try to carry out the following:

q Lower 2•f(f2)

q Select “Software wait is inserted.” (Refer to section “12.2 Software wait.”)

q Use the ready function. (Refer to section “12.3 Ready function.”)

Figure 17.1.6 shows a ready generating circuit example (with no wait). Figure 17.1.7 shows a ready

generating circuit example (with wait 1).

Note that the ready function is also valid for the internal area. Therefore, in Figures 17.1.6 and 17.1.7,

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areas where the ready function is valid are specified by using the chip select signal (CS2) which is

externally generated.

17.1 Memory expansion

7733 Datasheet(PDF) 417 Page - Renesas Technology Corp