Page 105 - Mechatronic Systems Modelling and Simulation with HDLs

94 5 SOFTWARE IN HARDWARE DESCRIPTION LANGUAGES

range of initialisations are necessary, such as, for example, filling the memory with
the programme, resetting the register and jumping to the first instruction.
If the C routine has been called before, the correct context must first of all
be created. If it is a replay the old stored context is activated by exchanging
(exchange_context) with the current context. Then the old context is always
protected by copying (copy_context). The jumptothe hub brings about a jump
to the instruction referred to in the programme counter of the current context.
The lda, jsr and bra instructions from the assembler programme can also be
found in the C routine. There are called by labels (l256, l258, l261), which
permit jumping to the instructions using the goto command.
First the lda should be considered more closely. Depending upon the targetted
address this command fetches a value from the memory or from a port and stores
it in the accumulator. First a routine is called up for this instruction, which controls
the debugger and thus permits it to visualise the software sequence, indicate values,
and control the software sequence by means of breakpoints. The user interface of
the debugger is shown in Figure 5.7. The next instruction decides whether the

Figure 5.7 Software debugger for virtual hardware