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USER’S GUIDE
050396 20/173
21
On occasion, a memory mapped peripheral is needed
that interfaces directly to an 8051 multiplexed bus.
When this occurs, MOVX instructions can be forced to
use the Expanded bus in any mode with the EXBS bit
(RPCTL.5). Setting this bit to a logic one forces all
MOVX instructions to the Expanded bus. While
EXBS=1, the entire 64K data memory map is accessed
in this way. Clearing EXBS will cause the microcontrol-
ler to revert to its selected configuration. In most sys-
tems, the EXBS bit will not be used.
PERIPHERAL ENABLES IN THE DATA MEMORY MAP Figure 4–7
DATA
MEMORY
PES=1
PE1
PE2
PE3
PE4
FFFFh
BFFFh
7FFFh
3FFFh
64K
0
DS5001/DS5002 Memory Map Control
Like the DS5000, the DS5001/DS5002 uses Special
Function Registers to control the memory map. The
memory control functions include the Partition, Range,
Partition Mode (PM), Expanded Bus Select (EXBS), Pe-
ripheral Enable Select (PES) and Access Enable (AE –
discussed below). The Partition and Range can be se-
lected using the Bootstrap Loader discussed in a later
section. In addition, the Partition can be selected or mo-
dified by the application software by writing to the
MCON register. PES is normally used by software and is
also controlled by the MCON register. The MCON is
documented in the SFR summary, but also appears
here for convenience. The Range is controlled by a
combination of MCON and RPCTL bits. In addition, the
EXBS and AE are controlled using the RTPCL register.
As not all of the RPCTL bits pertain to memory control,
the relevant bits are described below. RPCTL is fully
documented in the SFR summary.