Specifications

13
3706C–MICRO–2/11
AT89LP3240/6440
3.2.2 IDATA
The full 256 byte internal RAM can be indirectly addressed using the 8-bit pointers R0 and R1.
The first 128 bytes of IDATA include the DATA space. The hardware stack is also located in the
IDATA space when XSTK = 0.
3.2.3 SFR
The upper 128 direct addresses (80H–FFH) access the I/O registers. I/O registers on AT89LP
devices are referred to as Speci
al Function Registers. The SFRs can only be accessed through
direct addressing. All SFR locations are not implemented. See Section 4. for a listed of available
SFRs.
3.3 External Data Memory
AT89LP microcontrollers support a 16-bit external memory address space for up to 64K bytes of
external data memory (XDATA). The external memory space is accessed with the MOVX
instructions. Some internal data memory resources are mapped into portions of the external
address space as shown in Figure 3-3. These memory spaces may req
uire configuration before
the CPU can access them. The AT89LP3240/6440 includes 4K bytes of on-chip Extra RAM
(EDATA) and 8K bytes of nonvolatile Flash data memory (FDATA).
Figure 3-3. External Data Memory Map
3.3.1 XDATA
The external data memory space can accommodate up to 64KB of external memory. The
AT89LP3240/6440 uses the standard 8051 external memory interface with the upper address
b
yte on Port 2, the lower address byte and data in/out multiplexed on Port 0, and the ALE, RD
and WR strobes. MOVX instructions targeted to XDATA requ ire a minimum of 4 clock cycles.
XDATA can be accessed with both 16-bit (MOVX @DPTR) and 8-b it (MOVX @Ri) addresses.
See Section 3.3.4 on page 17 for more details of the external memory interface.
Extra RAM
(EDATA: 4KB)
0FFF
2FFF
3000
Flash Data
(FDATA: 8KB)
0000
0FFF
1000
FFFF
External Data
(XDATA: 64KB)
External Data
(XDATA: 60KB)
Extra RAM
(EDATA: 4KB)
External Data
(XDATA: 52KB)
FFFF FFFF
1000
EXRAM = 1 EXRAM = 0
DMEN = 0
EXRAM = 0
DMEN = 1