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MIPS cJTAG User Manual

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MIPS® cJTAG Adapter User's Manual

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Summary of Contents for MIPS cJTAG

  • Page 1 MIPS® cJTAG Adapter User’s Manual...
  • Page 2 MIPS provides a cJTAG Adapter IP block that converts a 2-pin 1149.7 (also known as cJTAG) to the 4-pin 1149.1 debug interface present on MIPS cores. The IP resides outside the core and is treated as a separate IP block from the point of view of design verification and implementation.
  • Page 3 The CP is 0000. At the rising edge of TCKC in the last bit of the CP, the Adapter is activated. From that point forward, activity on TCKC/TMSC is interpreted as Oscan1 format, described in the IEEE Standard, until the Adapter is reset or otherwise taken offline. MIPS® cJTAG Adapter User’s Manual, Revision 01.00...
  • Page 4 To avoid a drive conflict in Advanced Protocol (Oscan1), TMSC is driven by its source only while TCKC is low, and relies on a system-level keeper circuit to maintain a valid logic level while TCKC is high. Figure 4 cJTAG Online Activation Code TCKC TMSC-probe nTDI nTDI nTDI TMSC-device SYS_TCK SYS_TDI SYS_TMS SYS_TDO MIPS® cJTAG Adapter User’s Manual, Revision 01.00...
  • Page 5 MIPS CPU Core and the cJTAG Adapter. An nTRST signal can be provided in the same way for cJTAG and EJTAG interfaces, that is, it can be provided exter- nally as an input pin to the SoC, or it can be generated internally by the SoC in order to reset the TAP circuitry using on-chip power-on reset logic.
  • Page 6 TCKC SYS_TCK For the rest of the cJTAG signals TMSC_*, they should be constrained in a similar way as input TDI and TMS, and output TDO, like in the 4-wire EJTAG interface when the cJTAG Adapter is not in used.

  • Page 7: Revision History

    To see how the adapter works, TAP-related test cases such as ‘tap_fastdata-ebm32k-cjtag-zws’ can be run under a normal softcore testbench environment. Without the ‘-cjtag-’ mode string, the test cases will run with the normal EJTAG (IEEE1149.1) interface, bypassing the Adapter.
  • Page 8 MIPS and MIPS’ affiliates do not assume any liability arising out of the application or use of this information, or of any error or omission in such information.

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