User manual

Debug for 8- and 16-Bit Devices

FIGURE 7-2: BUILD OPTIONS TRACE TAB – NATIVE TRACE SELECTION

The trace and log information transmitted is identical regardless of the trace method

used. For TRACE(), a single value in the range of 64-127 is sent. A label generated

using this number is automatically inserted into the code so MPLAB IDE can identify in

the trace buffer the location which sent the value. For LOG(), a two-byte header is sent

followed by the value of the variable being logged. The first byte indicates the variable

type and is a value between 0 and 63. The second byte indicates the location which

sent the variable. Here, the location is represented by a value between 0 and 127. (See

Section 7.3.10 “More on Trace/Log ID Numbers”.)

Interrupts are disabled during every TRACE() and LOG() call. This is to ensure that

trace or log statements at an interrupt level do not interfere with a trace or log statement

that may already be in progress at the application level. A similar argument holds for

protecting statements within a low priority interrupt from being corrupted by ones from

a high priority interrupt.

7.3.3 Types of Trace

Currently there are three types of trace. All types are language tool version dependent

and stream data real-time to MPLAB IDE.

The pluses and minuses of using each trace type, as well as the type of communication

available (standard and/or high-speed), are summarized below.

Type of Trace

Trace Usage Communication

Advantage Disadvantage Std HS

Native Trace No dedicated pins

needed.

Device must have built-in

debug circuitry.

15 MIPS

or less

Greater than

15 MIPS

I/O Port Trace Fastest trace

method.

An 8-bit port must be

dedicated to trace.

Yes

(1)

Yes

(1)

SPI Trace Faster than Native

Trace.

SPI pins must be dedicated

to trace.

No Yes

Note 1: Also requires connection from device port to emulator logic probe port.