MAC7200 datasheet(245/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

167

Message will be queued. The error encoding will indicate which type(s) of messages attempted to be

queued while the FIFO was being emptied.

If only an OTM Message attempts to enter the queue while it is being emptied, the Error Message will

incorporate the OTM only error encoding (00000). If both OTM AND either BTM or DTM messages

attempt to enter the queue, the Error Message will incorporate the OTM and Program Trace error encoding

(00111). If a Watchpoint also attempts to be queued while the FIFO is being emptied, then the Error

Message will incorporate error encoding (01000).

NOTE

The OVC bits within the DC Register can be set to delay the CPU by

asserting the FIFOFULL signal in order to alleviate (but not eliminate)

potential overruns.

Error information is messaged out in the following format (see Table 11-2).

11.11.1.3 OTM Flow

Ownership Trace Messages are generated when the operating system writes to the memory mapped

Ownership Trace Register.

The following flow describes the OTM process.

1. For the A7S Nexus3 module, the OTR register is a memory mapped register, whose address is

located in the UBA. The UBA is internal to the Nexus module and can be accessed by the

IEEE-ISTO 5001 tool through the JTAG port.

2. Only word writes to the OTR are valid. The data value written into the OTR is registered and

formed into the Ownership Trace Message that is queued to be transmitted.

3. OTR reads do not cause Ownership Trace Messages to be transmitted by the A7S Nexus3 module.

11.11.2 Program Trace

This section details the program trace mechanisms supported by Nexus 3 for the ARM7 processor.

Program trace is implemented via Branch Trace Messaging (BTM) as per the Class 2 IEEE-ISTO 5001

standard definition.

11.11.2.1 Branch Trace Messaging (BTM)

Traditional Branch Trace Messaging (Thumb mode only) facilitates program trace by providing the

following types of information:

(5 bits)

(4 bits)

(6 bits)

ERROR (00000 / 00111 / 01000)

SRC

TCODE (001000)

Fixed length = 15 bits

Figure 11-25. Error Message Format

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