5.4 DB

Define constant byte(s) in program memory and EEPROM.

The DB directive reserves memory resources in the program memory or the EEPROM memory. In order to be able to refer to the reserved locations, the DB directive should be preceded by a label. The DB directive takes a list of expressions, and must contain at least one expression. The DB directive must be placed in a Code Segment or an EEPROM Segment.

The expression list is a sequence of expressions, delimited by commas. Each expression must evaluate to a number between -128 and 255. If the expression evaluates to a negative number, the 8-bits twos complement of the number will be placed in the program memory or EEPROM memory location.

If the DB directive is given in a Code Segment and the expression-list contains more than one expression, the expressions are packed so that two bytes are placed in each program memory word. If the expression-list contains an odd number of expressions, the last expression will be placed in a program memory word of its own, even if the next line in the assembly code contains a DB directive. The unused half of the program word is set to zero. A warning is given, in order to notify the user that an extra zero byte is added to the .DB statement.

Syntax
LABEL: .DB expressionlist
Example
.CSEG 
consts: .DB 0, 255, 0b01010101, -128, 0xaa

.ESEG 
const2: .DB 1,2,3