MAC7200 datasheet(220/976 Pages) FREESCALE

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Nexus Application Usage

MAC7200 Microcontroller Family Reference Manual, Rev. 2

142

Freescale Semiconductor

3. Drive the JTAG TAP State Machine into the Test-Logic-Reset state. While the State Machine is in

this state, all Nexus output pins are driven to their off value

4. Drive the EVTI pin high (negated)

5. Drive the JTAG TAP State Machine out of the Test-Logic-Reset state (into the Run-Test/Idle state

for instance)

Note that the Nexus is always in a disabled state after a Power On Reset. Once the Nexus module has been

disabled, it will remain disabled until explicitly enabled.

When the Nexus is disabled the Nexus outputs have the following off values:

In the disabled state, all Nexus3 registers are not accessible for reads or writes. In addition, the EVTI input

is ignored, except when exiting the Test-Logic-Reset state, as described in Section 11.8.3, “Resetting

Nexus.

11.8.6

Nexus Development Status (DS) Register

The DS implementation on the MAC72xx is identical to the MAC71xx, except that the MAC72xx does

not support STOP mode, so the DS[28] bit should always read back 0.

The DS[29] is for DOZE mode and the DS[30] is for Debug mode, which on the MAC72xx is identical to

the ARM7 Debug Mode (DS[31]).

The DS[27:26] bits are tied low (0), and DS[25:24] are unused and read back 0b00. This gives the

following possible combinations for DS[31:24]:

11.8.7

Unintended Activation of Nexus

If the Nexus is not intended to be used, the PF1 pin should be driven low at reset. This will disconnect all

Nexus outputs, and force the EVTI input to the Nexus high (disabled). It is still possible to activate the

Nexus through the JTAG interface in this case. However, there will be no impact to the value of the pins

on either Nexus port.

EVTO

MSEO

RDY

MCKO

MDO[n]

$00

Entering Normal Mode

$20

Entering Doze mode from Normal Mode

$C0

Entering Debug Mode from Normal Mode

$E0

Entering Debug Mode from Doze Mode or Doze Mode

from Debug Mode

MAC7200 Datasheet(PDF) 220 Page - Freescale Semiconductor, Inc

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