SONIX SN8P2501D - Jump Table Description

SN8P2501D
8-Bit Micro-Controller
SONiX TECHNOLOGY CO., LTD Page 17 Version 1.5
2.1.4 JUMP TABLE DESCRIPTION
The jump table operation is one of multi-address jumping function. Add low-byte program counter (PCL) and ACC
value to get one new PCL. If PCL is overflow after PCL+ACC, PCH adds one automatically. The new program counter
(PC) points to a series jump instructions as a listing table. It is easy to make a multi-jump program depends on the
value of the accumulator (A).
 Note: PCH only support PC up counting result and doesn’t support PC down counting. When PCL is
carry after PCL+ACC, PCH adds one automatically. If PCL borrow after PCL–ACC, PCH keeps value and
not change.
 Example: Jump table.
ORG
0X0100
; The jump table is from the head of the ROM boundary
B0ADD
PCL, A
; PCL = PCL + ACC, PCH + 1 when PCL overflow occurs.
JMP
A0POINT
; ACC = 0, jump to A0POINT
JMP
A1POINT
; ACC = 1, jump to A1POINT
JMP
A2POINT
; ACC = 2, jump to A2POINT
JMP
A3POINT
; ACC = 3, jump to A3POINT
SONIX provides a macro for safe jump table function. This macro will check the ROM boundary and move the jump
table to the right position automatically. The side effect of this macro maybe wastes some ROM size.
 Example: If “jump table” crosses over ROM boundary will cause errors.
@JMP_A
MACRO
VAL
IF
(($+1) !& 0XFF00) !!= (($+(VAL)) !& 0XFF00)
JMP
($ | 0XFF)
ORG
($ | 0XFF)
ENDIF
B0ADD
PCL, A
ENDM
 Note: “VAL” is the number of the jump table listing number.
 Example: “@JMP_A” application in SONIX macro file called “MACRO3.H”.
B0MOV
A, BUF0
; “BUF0” is from 0 to 4.
@JMP_A
5
; The number of the jump table listing is five.
JMP
A0POINT
; ACC = 0, jump to A0POINT
JMP
A1POINT
; ACC = 1, jump to A1POINT
JMP
A2POINT
; ACC = 2, jump to A2POINT
JMP
A3POINT
; ACC = 3, jump to A3POINT
JMP
A4POINT
; ACC = 4, jump to A4POINT