Datasheet

Product data sheet Rev. 6 — 14 June 2011 22 of 41

NXP Semiconductors

LPC2194

Single-chip 16/32-bit microcontroller

when an application does not require any peripherals to run at the full processor rate.

Because the APB divider is connected to the PLL output, the PLL remains active (if it was

running) during Idle mode.

6.19 Emulation and debugging

The LPC2194 support emulation and debugging via a JTAG serial port. A trace port allows

tracing program execution. Debugging and trace functions are multiplexed only with

GPIOs on Port 1. This means that all communication, timer and interface peripherals

residing on Port 0 are available during the development and debugging phase as they are

when the application is run in the embedded system itself.

6.19.1 EmbeddedICE

Standard ARM EmbeddedICE logic provides on-chip debug support. The debugging of

the target system requires a host computer running the debugger software and an

EmbeddedICE protocol convertor. EmbeddedICE protocol convertor converts the Remote

Debug Protocol commands to the JTAG data needed to access the ARM core.

The ARM core has a Debug Communication Channel function built-in. The debug

communication channel allows a program running on the target to communicate with the

host debugger or another separate host without stopping the program flow or even

entering the debug state. The debug communication channel is accessed as a

co-processor 14 by the program running on the ARM7TDMI-S core. The debug

communication channel allows the JTAG port to be used for sending and receiving data

without affecting the normal program flow. The debug communication channel data and

control registers are mapped in to addresses in the EmbeddedICE logic.

The JTAG clock (TCK) must be slower than

⁄

of the CPU clock (CCLK) for the JTAG

interface to operate.

6.19.2 Embedded trace macrocell

Since the LPC2194 have significant amounts of on-chip memory, it is not possible to

determine how the processor core is operating simply by observing the external pins. The

Embedded Trace Macrocell (ETM) provides real-time trace capability for deeply

embedded processor cores. It outputs information about processor execution to the trace

port.

The ETM is connected directly to the ARM core and not to the main AMBA system bus. It

compresses the trace information and exports it through a narrow trace port. An external

trace port analyzer must capture the trace information under software debugger control.

Instruction trace (or PC trace) shows the flow of execution of the processor and provides a

list of all the instructions that were executed. Instruction trace is significantly compressed

by only broadcasting branch addresses as well as a set of status signals that indicate the

pipeline status on a cycle by cycle basis. Trace information generation can be controlled

by selecting the trigger resource. Trigger resources include address comparators,

counters and sequencers. Since trace information is compressed the software debugger

requires a static image of the code being executed. Self-modifying code can not be traced

because of this restriction.