DECLARE

V_STRING        VARCHAR2(30):='Ascii Test';
V_ASCII         VARCHAR2(500);

BEGIN

    FOR i IN 1..LENGTH(V_STRING) LOOP
    
     V_ASCII:= V_ASCII || '|' || ASCII(SUBSTR(V_STRING,i,1));  
    
    END LOOP;
    
  dbms_output.put_line(v_ascii);  

END;

SQL> select replace(substr(dump('Ascii Test'),instr(dump('Ascii Test'),':')+2),',','|') res from dual;
RES
-----------------------------------
65|115|99|105|105|32|84|101|115|116

SQL> select rtrim(xmlagg(xmlelement (e, ascii(substr('Ascii Test', level, 1)) ||';')).
  2         extract ('//text()'), ';') result
  3  from dual
  4  connect by level <= length('Ascii Test');

RESULT
--------------------------------------------------------------------------------
65;115;99;105;105;32;84;101;115;116

SQL>