Epson S5U1C63000A, Руководство пользователя

Страница: 94 / 346

CHAPTER 4: ASSEMBLER
80
EPSON
S5U1C63000A MANUAL
(S1C63 FAMILY ASSEMBLER PACKAGE)
4.7.11 Area Securing Pseudo-Instructions (.comm, .lcomm)
Instruction format
.comm <Symbol>[,] <Size>
.lcomm <Symbol>[,] <Size>
<Symbol>:
Symbols for data memory access (address reference)
• The 1st character is limited to a–z, A–Z, ? and _.
• The 2nd and the subsequent character can use a–z, A–Z, 0–9, ? and _.
• Uppercase and lowercase are discriminated.
When assembling with the "-c" option, all symbols are case insensitive.
• One or more spaces or tabs are necessary between instruction and symbol.
<Size>:
Number of words of the area to be secured (4 bits/word)
• Only decimal, binary and hexadecimal numbers can be described.
• The size that can grammatically be specified is from 0 to 65,534.
• One or more spaces, tabs or a comma (,) are necessary between symbol and size.
Sample description:
.bss
.comm RAM0 4
.lcomm BUF,1
Function
Sets an area of the specified size in the BSS section (RAM and other data memory), and creates a
symbol indicating its top address with the specified name. By using this symbol, you can describe an
instruction to access the RAM.
Difference between .comm and .lcomm
The .comm pseudo-instruction and the .lcomm pseudo-instruction are exactly the same in function,
but they do differ from each other in the scope of the symbols they create. The symbols created by the
.comm
pseudo-instruction become global symbols, which can be referred to externally from other
modules (however, the file to be referred to needs to be specified by the .global pseudo-instruction.)
The symbols created by the .lcomm pseudo-instruction are local symbols, which cannot be referred to
from other modules.
Precaution
The .comm and .lcomm pseudo-instructions can only be described in BSS sections.