71m6545h-igtr/f Maxim Integrated Products, Inc., 71m6545h-igtr/f Datasheet - Page 32

• Manufacturer Part Number: 71m6545h-igtr/f
• Description: Metrology Processors
• Manufacturer: Maxim Integrated Products, Inc.

SFR. This method allows the user paged access (256 pages of 256 bytes each) to all ranges of the
external data RAM.
In the second type of MOVX instruction, MOVX A,@DPTR, the data pointer generates a 16-bit address.
This form is faster and more efficient when accessing very large data arrays (up to 64 KB), since no
additional instructions are needed to set up the eight high ordered bits of the address.
It is possible to mix the two MOVX types. This provides the user with four separate data pointers, two
with direct access and two with paged access, to the entire 64 KB of external memory range.
Dual Data Pointer
The Dual Data Pointer accelerates the block moves of data. The standard DPTR is a 16-bit register that
is used to address external memory or peripherals. In the 80515 core, the standard data pointer is called
DPTR, the second data pointer is called DPTR1. The data pointer select bit, located in the LSB of the DPS
register (DPS[0], SFR 0x92), chooses the active pointer. DPTR is selected when DPS[0] = 0 and DPTR1 is
Data Sheet 71M6545/H
MOVX Addressing
There are two types of instructions differing in whether they provide an 8-bit or 16-bit indirect address to
the external data RAM.
In the first type, MOVX A,@Ri, the contents of R0 or R1 in the current register bank provide the eight
lower-ordered bits of address. The eight high-ordered bits of the address are specified with the PDATA
selected when DPS[0] = 1.
The user switches between pointers by toggling the LSB of the DPS register. The values in the data pointers
are not affected by the LSB of the DPS register. All DPTR related instructions use the currently selected
DPTR for any activity.
An alternative data pointer is available in the form of the PDATA register (SFR 0xBF), sometimes referred
to as USR2). It defines the high byte of a 16-bit address when reading or writing XDATA with the instruction
MOVX A,@Ri or MOVX @Ri,A.
Internal Data Memory Map and Access
The Internal data memory provides 256 bytes (0x00 to 0xFF) of data memory. The internal data memory
address is always 1 byte wide.
The Special Function Registers (SFR) occupy the upper 128 bytes. The SFR area of internal data memory
is available only by direct addressing. Indirect addressing of this area accesses the upper 128 bytes of
Internal RAM. The lower 128 bytes contain working registers and bit addressable memory. The lower 32
bytes form four banks of eight registers (R0-R7). Two bits on the program memory status word (PSW, SFR
0xD0 ) select which bank is in use. The next 16 bytes form a block of bit addressable memory space
32
0000-13FF
2000-27FF
2800-287F
0000-00FF
DPTR1 is useful for copy routines, where it can make the inner loop of the routine two instructions faster
compared to the reloading of DPTR from registers. Any interrupt routine using DPTR1 must save and
restore DPS, DPTR and DPTR1, which increases stack usage and slows down interrupt latency.
By selecting the Evatronics R80515 core in the Keil compiler project settings and by using the compiler
directive “MODC2”, dual data pointers are enabled in certain library routines.
The second data pointer may not be supported by certain compilers.
Static RAM
Static RAM
Static RAM
Static RAM
© 2008–2011 Teridian Semiconductor Corporation
Table 10
Non-volatile
(battery)
Volatile
Volatile
Volatile
shows the internal data memory map.
RAM (I/O RAM)
RAM (I/O RAM)
External RAM
Configuration
Configuration
Internal RAM
(XRAM)
Part of 80515 Core
(on 1 KB boundary)
Shared by CE and
Hardware control
Battery-buffered
memory
MPU
PDS_6545_009
5 KB
2 KB
128
256
v1.0