MAC7200 datasheet(209/976 Pages) FREESCALE

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Introduction

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

131

11.1.3

Modes of Operation

There are three (3) basic modes of operation for the A7S Nexus3 block.

•Reset

•

Normal

•

Disabled

11.1.3.1

Reset

The reset configuration is received via the EVTI pin to enable or disable the A7S Nexus3 module. EVTI

is sampled synchronously at the exit from the JTAG Test-Logic-Reset state. Reset configuration

information must be valid on EVTI during the JTAG “Test Logic Reset” state (see 11.12, “IEEE 1149.1

State Machine and RD/WR Sequences”).

The A7S Nexus3 module will disable (drive inactive) the output pins during the JTAG Test-Logic-Reset

state or when a Power-on-Reset (POR) event occurs.

11.1.3.2

Normal

If EVTI is asserted at the exit from JTAG Test-Logic-Reset, the A7S Nexus3 module will be enabled. The

module will be ready to accept control input via the JTAG pins.

The A7S Nexus3 module may also be enabled by loading the NEXUS-ACCESS instruction into the JTAG

Instruction Register. Once the A7S Nexus3 module has been enabled, it will remain enabled until entry

into the JTAG Test-Logic-Reset state.

11.1.3.3

Disabled

If EVTI is negated at the exit from JTAG Test-Logic-Reset, the A7S Nexus3 module will be disabled. No

trace output will be provided, auxiliary port output pins (MDO, MSEO, MCKO) will be disabled (driven

inactive), and Nexus3 registers will not be accessible for reads or writes.

NOTE

If there is no debug/development tool connected to the SoC, the EVTI pin

should be held de-asserted in order to keep the Nexus3 module disabled.

The A7S Nexus3 module may be enabled after the exit from JTAG Test-Logic-Reset state by loading the

NEXUS-ACCESS instruction into the JTAG Instruction Register.

11.1.4

TCODEs supported

The A7S Nexus3 pins allow for flexible transfer operations via Public Messages. A TCODE defines the

transfer format, the number and/or size of the packets to be transferred, and the purpose of each packet.

The IEEE-ISTO 5001 standard defines a set of public messages. The A7S Nexus3 block supports the

public TCODEs seen in Table 11-1.

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