Echelon Neuron - Manual (Page 167)

SEG (Segment Control)
The SEG directive controls the currently open segment type. Any of the
supported segment types (including the one that is currently active) can be
selected. The active segment selection can be changed as needed.
The assembler groups assembly instructions and data blocks into one or more
segments. A segment is a group of assembly instructions and data blocks that are
assembled into consecutive bytes of machine instructions and data, at
consecutive and ascending addresses. The basic unit for the assembler is a
statement, but the basic unit for the linker is a segment. The linker relocates
code and data on a segment-by-segment basis.
During assembly:
• One segment of each type is always open.
• Additional code and data can be added only to an open segment.
• Only one of the open segments is the currently active segment.
• The next assembly instruction or data statement encountered in the
assembly file is added to the active segment.
The segment type does not affect the assembly of the source lines within it, but
does affect the linking of the segment.
The SEG directive does not cause additional segments to be opened, but instead
selects which of the open segments is active. When the assembler starts, it opens
an empty, relocatable segment of each type, and selects the ROM segment as the
active segment. Thus, the simplest assembly files need not use either a SEG or
ORG directive if only a single ROM segment is needed.
Typical assembly programs use SEG CODE for code and constant data, SEG
RAMFAR or RAMNEAR for RAM variables, and EEFAR or EENEAR for non-
volatile, persistent, variables.
See also ORG (Segment Control).
Syntax:
The SEG directive requires one argument for the type of segment that is being
made active. This directive cannot have a label.
SEG CODE
SEG EECODE
SEG EEFAR
SEG EENEAR
SEG INITCODE
SEG RAMCODE
SEG RAMFAR
SEG RAMNEAR
SEG ROM
SEG SIDATA
Segment type names can be specified in either lower or upper case. See Segments
for information about the segment types.
Neuron Assembly Language Reference 157