Zilog ZUSBOPTS - Manual (Page 339)

UM017105-0511 Program Configurations
Zilog Developer Studio II – ZNEO™
User Manual
311
segment NEAR_BSS
val: dl %12345678 ; incorrect usage for production code, as RAM does
; not retain value across power cycles: NOT OK
If your application has a lot of such initializations, this approach can be tedious. In
that case, an alternative is to use the linker COPY directive and perform the physical
copy for all of the RAM data as a single loop in the startup. An example can be found
in the C startup provided in the installation under
src\boot\common\start-
ups.asm :
;
; Copy ROM data into internal RAM
;
LEA R0,_low_near_romdata
LEA R1,_low_neardata
LD R2,#_len_neardata+1
JP lab10
lab9:
LD.B R3,(R0++)
LD.B (R1++),R3
lab10:
DJNZ R2,lab9
The installation also includes the following linker directives:
COPY NEAR_DATA EROM
define _low_near_romdata = copy base of NEAR_DATA
define _low_neardata = base of NEAR_DATA
define _len_neardata = length of NEAR_DATA
In the above linker directives, NEAR_DATA is the RAM segment containing initialized
data:
segment NEAR_DATA
val1: dl %12345678
val2: dl %23456789
val3: dl %3456789A
…
The linker COPY directive only designates the load addresses and the run-time
addresses for the segments. The actual copying of the data must be performed by the
user code as shown above.
•
Assembly users can perform their own external interface setup in the start-up code.
This can be made easier if you take advantage of some definitions provided by the
Configure Target dialog box (see the
Setup section on page 76). An example can be
found in the C startup provided in the installation under src\boot\com-
mon\startupexs.asm . The ZDS II IDE generates the following linker directives
based on your settings in the Target Configure dialog box:
DEFINE __EXTCT_INIT_PARAM = $c0