NEC 78014Y Series, User Manual

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CHAPTER 19 EXTERNAL DEVICE EXPANSION FUNCTION
482
19.4 Example of Memory Connection
An example of external memory connection with the
µ
PD78014 is shown in Figure 19-7. SRAM is used as the
external memory in this application example. In addition, the external device expansion function is used in the full-
address mode, and the internal ROM is allocated to addresses 0000H to 7FFFH (32 Kbytes), and SRAM is allocated
to addresses above 8000H.
Figure 19-7. Example of Memory Connection with
µ
PD78014
Caution At the external memory read modify write timing, the time from RD signal rising to write data output
is very short, so that the write data sometimes conflicts with the output data from external memory
(SRAM, etc). In this case, it is possible to avoid data conflict by not using the following instructions
which generate read modify write timing.
XCH A, !addr16 XCH A, [HL + C]
XCH A, [DE] MOV1 [HL].bit, CY
XCH A, [HL] SET1 [HL].bit
XCH A, [HL + byte] CLR1 [HL].bit
XCH A, [HL + B] BTCLR [HL].bit, $addr16
RD
WR
A8 to A14
ASTB
AD0 to AD7
V
DD
PD74HC573
LE
Q0 to Q7
D0 to D7
Address bus
PD43256B
CS
OE
WE
A0 to A14
Data bus
PD78014
OE
I/O1 to I/O8
µ
µ
µ