MAC7200 datasheet(219/976 Pages) FREESCALE

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Nexus Application Usage

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

141

Control Register (PCR) in the Nexus (0 = 1-pin, 1 = 2-pin). On the MAC72xx, a single MSEO pin is

available. Therefore, the software must not set this bit in the PCR register.

11.8.2

Programming the PCR Register

In order to match the hardware implementation of the Nexus3p on the MAC72xx, the following PCR

11.8.3

Resetting Nexus

Resetting the Nexus3p is done as described in the Nexus Block Guide, by taking the JTAG TAP State

Machine into the Test-Logic-Reset state. There is no minimum required time that this state has to be held.

Please also refer to Chapter 6, “Resets” for information on resetting Nexus.

11.8.4

Enabling Nexus

In order to enable Nexus, you must perform one of the following methods:

Method #1

1. At reset, drive the PF1 pin high to enable a Nexus port

2. At reset, drive the PF0 pin low or high to select which Nexus port to use

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

4. Drive the EVTI pin low (asserted)

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

for instance)

Method #2

1. At reset, drive the PF1 pin high to enable a Nexus port

2. At reset, drive the PF0 pin low or high to select which Nexus port to use

3. Load the NEXUS_ACCESS instruction into the JTAG TAP State Machine

Once the Nexus module has been enabled, it will remain enabled until entry into the JTAG

Test-Logic-Reset state or a Power On Reset is performed.

11.8.5

Disabling Nexus

In order to disable Nexus, you must perform the following:

1. At reset, drive the PF1 pin low to disable Nexus ports. The value driven on PF0 does not matter in

this case.

2. If a Power On Reset has been performed, and the Nexus was not enabled, then no further action is

necessary.

PCR[31:30]

PCR[25]

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