Rainbow Electronics AT89LP216 - Manual (Page 10)

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3621A–MICRO–6/06
AT89LP216 [Preliminary]
Figure 8-3. Two-cycle ALU Operation (Example: ADD A, #data)
8.1 Restrictions on Certain Instructions
The AT89LP216 is an economical and cost-effective member of Atmel's growing family of micro-
controllers. It contains 2K bytes of Flash program memory. It is fully compatible with the MCS-51
architecture, and can be programmed using the MCS-51 instruction set. However, there are a
few considerations one must keep in mind when utilizing certain instructions to program this
device. All the instructions related to jumping or branching should be restricted such that the
destination address falls within the physical program memory space of the device, which is 2K
bytes for the AT89LP216. This should be the responsibility of the software programmer. For
example, LJMP 7E0H would be a valid instruction, whereas LJMP 900H would not.
8.1.1 Branching Instructions
The LCALL, LJMP, ACALL, AJMP, SJMP, and JMP @A+DPTR unconditional branching instruc-
tions will execute correctly as long as the programmer keeps in mind that the destination
branching address must fall within the physical boundaries of the program memory size (loca-
tions 000H to 7FFH for the AT89LP216). Violating the physical space limits may cause unknown
program behavior. With the CJNE [...], DJNZ [...], JB, JNB, JC, JNC, JBC, JZ, and JNZ condi-
tional branching instructions, the same previous rule applies. Again, violating the memory
boundaries may cause erratic execution. For applications involving interrupts the normal inter-
rupt service routine address locations of the 8051 family architecture have been preserved.
8.1.2 MOVX-related Instructions, Data Memory
The AT89LP216 contains 128 bytes of internal data memory. RAM accesses to addresses
above 7FH will return invalid data. Furthermore, the stack depth is limited to 128 bytes, the
amount of available RAM. The Stack Pointer should not be allowed to point to locations above
7FH. External DATA memory access is not supported in this device, nor is external PROGRAM
memory execution. Therefore, no MOVX [...] instructions should be included in the program.
A typical 8051 assembler will still assemble instructions, even if they are written in violation of
the restrictions mentioned above. It is the responsibility of the user to know the physical features
and limitations of the device being used and to adjust the instructions used accordingly.
System Clock
Total Execution Time
Fetch Immediate Operand
T
1
T
2
T
3
ALU Operation Execute
Result Write Back
Fetch Next Instruction