AN4035 datasheet(11/42 Pages) STMICROELECTRONICS

11 / 42 page

AN4035

JTAG

Doc ID 022669 Rev 2

11/41

Figure 3.

Enabling JTAG/Nexus port access on a censored device

The steps to enable the debug port on a censored device are as follows:

After the RSTOUT pin has is negated, hold the device in system reset state using a

debugger or other tool.

While the device is being held in system reset state shift the 64-bit password into the

CENSOR_CTRL register (via the JTAG port using the JTAG

ENABLE_CENSOR_CTRL instruction. The JTAG serial password is compared against

the serial boot flash password from the flash shadow block.

If there is a match the Nexus client TAP controller enters normal operation mode and

the DISNEX flag in the SIU_CCR register is negated (for the SPC56xB and SPC56xP

families the flag NXEN in the SSCM_STATUS register is negated) indicating Nexus is

enabled. Upon negation of reset the debug / calibration tool is able to access the

device via NEXUS port and JTAG. If the JTAG serial password does not match the

serial boot flash password or the serial boot flash password is an illegal password then

the debug / calibration tool is not able to access the device. After the debug port is

enabled, the tool can access the censored device and can erase and reprogram the

shadow flash block in order to uncensor the device.

Compare

64-bit Password

JTAG Port Controller

CENSOR_CTRL register

Nexus client

TAP controller

Debug/Calibration Tool

Access

64-bit Password

Enable/disable

Censored Flash Array

Other Nexus Clients

•eDMA

• e200z3 processor

AN4035 Datasheet(PDF) 11 Page - STMicroelectronics