Siemens CPU 948 User Manual

9.4 Operations with the Base Address Register (BR Register)
Application The base address register (20 bits) allows you to calculate addresses
and use indirect register load and transfer operations without using the
ACCUs.
The memory location whose absolute address is calculated as the sum
of the BR register content plus a constant is accessed.
Absolute address = BR register content + constant
Operations
Operation Operand Function
MBR
ABR
Constant
(0H to
F FFFFH)
Constant
(-32 768 to
+32 767)
Load the BR register with a
20-bit constant
Add a 16-bit constant to the contents
of the BR register
Changing the BR register
•• The BR register is retained, when the program is continued in a
different block of the same program execution level due to a
jump statement (’JU FB’/’JC FB’).
•• The BR register is retained after nesting in a different program
execution level.
•• If a different program execution level is called by the system
program, the BR register is set to ’0’.
Table 9-6 Load and arithmetic operations with the BR register
Operations with the Base Address Register (BR Register)
CPU 948 Programming Guide
9 - 22 C79000-G8576-C848-04

Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English