APPLICATION
7721 Group User’s Manual
16–15
16.1 Memory connection
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When data is output from external memory before falling edge of E signal
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Because the external memory outputs data before the falling edge of the E signal, there is a
possibility that the tail of address collides with the head of data. In such a case, generate the
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external memory read signal (OE) by using E. (Refer to “Figure 16.1.11.”)
Fig. 16.1.11 Example of making data output timing delayed
When using external memory that outputs data for more than tpzx(E-DLZ/DHZ) after rising edge of
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E signal
Because the external memory outputs data for more than tpzx(E-DLZ/DHZ) after the rising edge of the
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E signal, there is a possibility that the tail of data collides with the head of address. In such a case,
try to carry out the following:
q Cut the tail of data output from the memory by using, for example, a bus buffer.
q Use the Mitsubishi’s memory chips that can be connected without a bus buffer.
Figures 16.1.12 to 16.1.15 show examples of using bus buffers and the timing charts. Table 16.1.6
lists the Mitsubishi’s memory chips that can be connected without a bus buffer. When using one
of these memory chips, timing parameters tDF and tdis(OE) listed below are guaranteed. Accordingly,
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no bus buffer is necessary for the system where the external memory’s read signal (OE) goes high
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within tpzx(E-DLZ/DHZ)-tDF (or tdis(OE)) [ns] after the rising edge of the E signal.
Table 16.1.6 Mitsubishi’s memory chips that can be connected without bus buffers
Note: Make sure that d
≥ 0 is satisfied when generating the external
memory read signal (OE).
External memory
output enable signal
(Read signal)
Address
ta(OE)
E
OE
Address output
External memory
data output
Specifications of
external memory
d
ten(OE)
Address
Data
Memory
Flash memory
SRAM
Type
M5M28F101AP, FP, J, VP, RV-85, -10
M5M28F102AFP, J, VP-85, -10
M5M5256DP, FP, KP, VP, RV-45LL, -45XL, -55LL, -55XL,
-70LL, -70XL
M5M5278DP, J-12
M5M5278DP, FP, J-15, -15L
M5M5278DP, FP, J-20, -20L
tDF/tdis(OE) (Maximum)
15 ns
(Guaranteed as kit.)
(Note)
6 ns
7 ns
8 ns
Note: tDF or tdis(OE) listed above is guaranteed when these memory chips are connected with the M37721.
When the user wants specifications of these memory chips, add a comment “tDF/tdis(OE) = 15 ns,
microcomputer and kit.”