ADUC: Addressing up to 16Mbytes of external data memory

Document created by analog-archivist Employee on Feb 23, 2016
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Can the ADuC microcontroller address up to 16Mbytes of external data memory. Is
so, how is it done?


The Microcontroller can address up to 16Mbytes of external data memory. If
access to more
than 64 Kbytes of RAM is desired, a feature unique to the microcontroller
allows addressing up to
16 Mbytes of external RAM simply by adding an additional latch on the Port 2
address bus.
On a standard 8051 as with the Microcontrollerr Port 0 (P0) serves as a
multiplexed address/data
bus. It emits the low byte of the data pointer (DPL) as an address, which is
latched by a pulse of
ALE prior to data being placed on the bus by the microcontroller (write
operation) or the SRAM
(read operation). Port 2 (P2) provides the data pointer page byte (DPP) to be
latched by ALE,
followed by the data pointer high byte (DPH). If no latch is connected to P2,
DPP is ignored by the
SRAM, and the 8051 standard of 64kByte external data memory access is