Table 3-5 Data Formats in Memory
When the stack is accessed in exception processing (to save or restore the program counter, code
page register, or status register), word access is always performed, regardless of the actual data
size. Similarly, when the stack is accessed by an instruction using the pre-decrement or post-
increment register indirect addressing mode specifying R7 (@–R7 or @R7+), which is the stack
pointer, word access is performed regardless of the operand size specified in the instruction. An
address error will therefore occur if the stack pointer indicates an odd address. Programs should
be coded so that the stack pointer always indicates an even address.
Table 3-6 shows the data formats on the stack.
Data Type Data Format
1-Bit (in byte
operand data)
1-Bit (in word
operand data)
Byte
Word
7
6543 2107
15 14 13 12 11 10 9 8
6543210
MSB LSB
MSB
LSB
Upper 8 bits
Lower 8 bits
Address n
Even address
Odd address
Address n
Even address
Odd address
70
43
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