User`s guide

3–2 Remote Debugging
Programming Guidelines
3.4 Programming Guidelines
The following sections describe the programming guidelines for remote debugging.
3.4.1 The Run-Time Environment
When a program is started by the Debug Monitor’s go command, it is started at the
appropriate IPL to enable real-time clock interrupts (usually IPL 4). If a program
does not install its own interrupt handler, then the Debug Monitor will handle all
interrupts. If a program does install its own interrupt handler using the Write System
Entry Address PAL call, then it must be prepared to handle all interrupts as described
in the following sections. When a program completes normally, the Debug Monitor
reinstalls its own interrupt handler.
3.4.2 Types of Programs
For the purposes of this chapter, programs may be classified into the following three
types:
• Programs that do not use the Ethernet or do not include their own interrupt
handler.
• Programs that do not use the Ethernet but do include their own interrupt handler.
• Programs that use the Ethernet.
3.4.2.1 Restriction
There is only one restriction for programs that do not use the Ethernet and that use
the Debug Monitor interrupt handler. Do not disable the real-time clock interrupt and
the Ethernet interrupts for long periods.
Long delays may cause Ladebug to behave as if there is a problem with the Ethernet
link to the target. If network delays are insignificant, Ladebug will tolerate periods of
up to ten seconds with interrupts disabled, although it will normally warn the user of
possible network problems if interrupts are disabled for more than a second.
Ethernet interrupts are disabled at IPL 3 or more, and real-time clock interrupts are
disabled at IPL 5 or more. Writing to the control registers of the Ethernet device or to
the real-time clock can also disable the interrupts. It is possible to set breakpoints or
to single step uninterruptible code. There is no restriction on the time that can be
spent at the breakpoint.