Command Line Options For Rts Calls; How To Save On-Chip Memory By Placing Rts Off-Chip - Texas Instruments TMS320C6000 Programmer's Manual

How to Save On-Chip Memory by Placing RTS Off-Chip

4.2 How to Save On-Chip Memory by Placing RTS Off-Chip
Table 4–1. Definitions
Term Means
Normal RTS Ordinary RTS functions. Example: strcpy
functions
Internal RTS Functions which implement atomic C operations such as divide or floating point math on the
functions C62x and C64x. Example: _divu performs 32-bit unsigned divide.
near calls Function calls performed with a ordinary PC-relative branch instruction. The destination of
such branches must be within 1 048 576 (0x100000) words of the branch. Such calls use 1
instruction word and 1 cycle.
far calls Function calls performed by loading the address of the function into a register and then
branching to the address in the register. There is no limit on the range of the call. Such calls
use 3 instruction words and 3 cycles.
4.2.1 How to Compile
Table 4–2. Command Line Options for RTS Calls
4-6
One of many techniques you might use to save valuable on-chip space is to
place the code and data needed by the runtime-support (RTS) functions in off-
chip memory.
Placing the RTS in off-chip memory has the advantage of saving valuable on-
chip space. However, it comes at a cost. The RTS functions will run much slow-
er. Depending on your application, this may or may not be acceptable. It is also
possible your application doesn't use the RTS library much, and placing the
RTS off-chip saves very little on-chip memory.
Make use of shell (cl6x) options for controlling how RTS functions are called:
Option
Default
–mr0
–mr1
By default, RTS functions are called with the same convention as ordinary
user-coded functions. If you do not use a –ml n option to enable one of large-
memory models, then these calls will be near. The option –mr0 causes calls
Internal RTS calls
Same as user
Near
Far
Normal RTS calls
Same as user
Near
Far