SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 31

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

2) Using Two Datapointers (Code for an SAB 80C517)
Initialization Routine
Action
Initialize DPTR6 with source pointer
Initialize DPTR7 with destination pointer
Table Look-up Routine under Real Time Conditions
Action
Save old source pointer
Load source pointer
Increment and check for end of table
(execution time not relevant for this
consideration)
Fetch source data byte from ROM table
Save source_pointer and load
destination_pointer
Transfer byte to destination address
Save destination pointer and restore old
datapointer
Total execution time (machine cycles)
The above example shows that utilization of the SAB 80C517’s multiple datapointers can make
external bus accesses two times as fast as with a standard 8051 or 8051 derivative. Here, four data
variables in the internal RAM and two additional stack bytes were spared, too. This means for some
applications where all eight datapointers are employed that an SAB 80C517 program has up to
24 byte (16 variables and 8 stack bytes) of the internal RAM free for other use.
Semiconductor Group
MOVC A,@DPTR
MOVX @DPTR, A
Code
PUSH DPSEL
MOV DPSEL, #06H
INC DPTR
CJNE…
…
MOV DPSEL, #07H
POP DPSEL
–
32
MOV DPSEL, #07H
Code
MOV DPSEL, #06H
MOV DPTR, #1FFFH
MOV DPTR, #2FA0H
External Bus Interface
Machine
Cycles
2
–
–
–
2
2
2
2
12
2