M-Byte Expansion Function; Read Timing; Write Timing - NEC PD78212 User Manual

µ PD78214 Sub-Series
A8-A15
(output)
AD0-AD7
ASTB (output)
RD (output)
A8-A15
AD0-AD7
(output)
ASTB (output)
WR (output)
Caution External devices cannot be mapped to the same addresses as those of the internal RAM area ( µ PD78213, µ PD78214, and µ PD78P214:
0FD00H to 0FEFFH, µ PD78212: 0FD80H to 0FEFFH) and SFR area (0FF00H to 0FFFFH, excluding the external SFR area (0FFD0H to
0FFDFH)).
When manipulating a space in which external device addresses overlap internal RAM or SFR addresses, the internal RAM or SFR
area is accessed automatically. In this case, the address signal is output, but the ASTB, RD, and WR signals are not output (these
signals remain inactive).

13.2.2 1M-Byte Expansion Function

When bit MM6 of the MM register is set to 1, an additional 960K-bytes of data memory can be used. Therefore,
a 1M-byte memory space is available. In this case, pins P60 to P63 output the highest address bits, A16 to A19.
Example: MOV MM, #47H ; Expansion to 1M bytes
MOV P6, #3H ; Latches the highest address information (select bank 3)
•
•
•
MOV A, &!2000H ; Load the contents of memory at 32000H into register A.
348
Fig. 13-3 Read Timing
Hi-Z Hi-Z
Lower address
(output)
Fig. 13-4 Write Timing
Hi-Z Hi-Z
Lower address
Higher address
Data (input)
Higher address
Data
Hi-Z
Hi-Z