bscan_selftest Directory Reference

Directory dependency graph for bscan_selftest:

Directories
	src

Detailed Description

Self-test for the JTAG / IEEE-1149.1 boundary-scan bookkeeping driver ra8_bscan (#138). No panel, SD card, touch or external JTAG fixture needed.

There is no such thing as a "real" boundary-scan demo on this chip. The TAP is driven by an external manufacturing fixture over TCK/TMS/TDI/TDO while RES is held low, and its four registers (JTIR / JTIDR / JTBPR / JTBSR) are not memory-mapped – HUM Ch 50.2.3 p 3259 is explicit that the CPU can neither read nor write them. Exercising the actual scan chain is therefore inherently external-tool work: a BSDL file plus a JTAG controller. What firmware can validate is its own contribution, the ra8_bscan bookkeeping object.

The app runs that contract on both its positive and negative paths: the hardwired device ID code 0x085DA447 (HUM Ch 50.2.2 p 3258), which is the value the external fixture should scan out over TDO and so is the firmware's authoritative cross-check against it; acceptance of the named JTIR opcodes and rejection of the reserved 4-bit ones (HUM Ch 50.2.1 p 3258); and the status and clear-mask guards. It halts on a FAIL banner before the PASS line can be reached, so the gate is exact.

Because the driver touches no hardware at all, the banner is byte-identical on host, emulator and silicon, which makes this an emulator/silicon equivalence check as much as a driver test. The same logic is covered from the other side by the host unit tests in tests/misc/src/test_ra8_bscan.c.