* <https://git.libre-soc.org/?p=soc.git;a=blob;f=src/soc/bus/simple_gpio.py;hb=HEAD>
* <https://git.libre-soc.org/?p=pinmux.git;a=blob;f=src/spec/testing_stage1.py;hb=HEAD>
* <https://git.libre-soc.org/?p=pinmux.git;a=blob;f=src/spec/simple_gpio.py;hb=HEAD>
+* ST Ericsson presentation on the GPIO subsystem: <https://ftp.libre-soc.org/Pin_Control_Subsystem_Overview.pdf>
+* Technical guide to JTAG: <https://www.corelis.com/education/tutorials/jtag-tutorial/jtag-technical-primer>
+* Presentation on JTAG: <http://www.facweb.iitkgp.ac.in/~isg/ADV-TESTING/SLIDES/5-JTAG.pdf>
+* Useful information on mandatory JTAG instructions: <https://www.corelis.com/education/tutorials/jtag-tutorial/jtag-technical-primer/#JTAG_Instructions>
The tasks initially set out by Luke in 2019 (bug 50 description):
1. All pad inputs and sim controlled input (output enables etc.) should be high.
1. All signals should be high.
+These test cases are performed by the "jtag_unit_test" with selected JTAG
+ instructions (SAMPLE or EXTEST), data to send via TDI, and expected TDO data
+vector. The TDO and TDI data is compared using asserts.
+
+NOTE: Currently the last test case's TDO data does not match the actual
+core/pad signal values. Not sure why the returned TDO is icorrect, however
+the signals are correct.
+
# Simple GPIO extension
The code from soc repo was taken and is being extended to support full gpio capability
TODO