MAC7200 datasheet(217/976 Pages) FREESCALE

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Nexus External Pins

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

139

11.5

Nexus External Pins

The external pin interface is flexible. The minimum number of pins necessary is 4 pins for a basic Program

Trace implementation, or a maximum of 13 for a full Program + Data Trace implementation. All pins total

must be made available on either a Primary or Secondary Nexus Port

11.5.1

MDO - Message Data (Output)

These pins provide the packet data for the trace messages. The Nexus module can be programmed to use

a minimum number of MDO pins (2) or a maximum number of MDO pins (8). Following are the minimum

requirements for the number of MDO pins:

•

Program Trace only (Class 2): 2 MDO pins. As a benchmark, the EEMBC suite of automotive

benchmarks was run on a M*CORE Nexus3 module using the 2-pin MDO option (only turning on

Program Trace), at 100MHz without buffer overflow.

•

Program and Data Trace (Class 3): 8 MDO pins

11.5.2

MSEO - Message Start/End (Active low output)

These pins indicate to the development tool when each packet within a message begins and ends. The

Nexus module supports two of these pins for higher throughput (bandwidth), but only one is necessary for

IEEE compliance. For a Program and Data Trace only module running @ 80MHz, only 1 MSEO pin is

necessary.

11.5.3

EVTI - Event In (Active low input)

This required pin is multi-faceted. Initially, it is used to enable Nexus (sampled during a Debug Reset). It

is also programmable to create a “synchronization” type message (giving the full address if the tool is lost),

or initiate a debug request to the ARM core.

11.5.4

EVTO - Event Out (Active low output)

This optional pin can be used by the development tool to trigger on certain events. EVTO can be

programmed to assert based on the occurrence of a watchpoint (defined within the ARM CPU), or upon

the entry into Debug Mode.

Table 11-11. Nexus External Pins

Signal

Description

MDO[7:0]

8-bit Message Data Out (2 required, 6 optional)

MSEO

Message Start/End Out

EVTI

Event In

EVTO

Event Out

MCKO

Message Clock Out

RDY

Ready (Output)

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