IDATA problem

NAME    SAMPLE

 PUBLIC  TXTBIT

PROG    SEGMENT CODE
CONST   SEGMENT CODE
VAR1    SEGMENT DATA
BITVAR  SEGMENT BIT
STACK   SEGMENT IDATA

        RSEG  STACK
        DS    10H  ; 16 Bytes Stack

        CSEG  AT   0
        USING   0  ; Register-Bank 0
; Execution starts at address 0 on power-up.
        JMP   START

        RSEG  PROG
; first set Stack Pointer
START:  MOV   SP,#STACK-1

; Initialize serial interface
; Using TIMER 1 to Generate Baud Rates
; Oscillator frequency = 11.059 MHz
        MOV   TMOD,#00100000B           ;C/T = 0, Mode = 2
        MOV   TH1,#0FDH
        SETB  TR1
        MOV   SCON,#01010010B

; clear TXTBIT to read form CODE-Memory
        CLR   TXTBIT

; This is the main program. It is a loop,
; which displays the a text on the console.
REPEAT:
; type message
        MOV   DPTR,#TXT

; repeat
        SJMP  REPEAT
;
        RSEG  CONST
TXT:    DB    'TEST PROGRAM',00H

; only for demonstration
        RSEG  VAR1
DUMMY:  DS    21H

; TXTBIT = 0 read text from CODE  Memory
; TXTBIT = 1 read text from XDATA Memory
        RSEG  BITVAR
TXTBIT: DBIT  1

        END