NEC PD17062 - Manual (Page 24)

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PD17062
2.6 TABLE REFERENCE
The table reference instruction is used to reference the constant data in program memory. If the MOVT
DBF, @AR instruction is executed, data at the program memory address specified in an address register is
placed in a data buffer (DBF).
Because each data item in program memory consists of 16 bits, the constant data placed in the data buffer
by the MOVT instruction also consists of 16 bits (four words). Because the address register consists of eight
bits, the MOVT instruction can reference a program memory address between 0000H and 00FFH.
When table referencing is executed, a single stack is used.
See Sections 8.1 and 10.3.
2.7 NOTES ON USING THE BRANCH INSTRUCTION AND SUBROUTINE CALL INSTRUCTION
The 17K series assembler (AS17K) detects an error if a program memory address (numeric address) is
directly specified in the operand of the branch instruction (BR) or subroutine call instruction (CALL).
The assembler provides this function to minimize the number of bugs arising from program modification.
Examples 1. Instruction causing an error
;
#
BR 0005H ; The assembler detects the error.
;
$
CALL 00F0H ;
2. Instruction causing no error
;
%
LOOP1: ; The BR or CALL instruction is executed for a label used in the
BR LOOP1 ; program.
; &
SUB1: ;
CALL SUB1 ;
;
(
LOOP2 LAB 0005H ; As a label type, 0005H is assigned to LOOP2.
BR LOOP2 ;
; )
BR. LD. 0005H ; The numeric value of the operand is converted to a label type.
; It is recommended that this method not be used to reduce
; the number of bugs.
For details, refer to the AS17K User’s Manual.