From: lkcl Date: Sun, 14 Nov 2021 18:15:53 +0000 (+0000) Subject: (no commit message) X-Git-Tag: opf_rfc_ls005_v1~3390 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1855519e9697626612d224151ad6f2974c3121f3;p=libreriscv.git --- diff --git a/docs/pinmux.mdwn b/docs/pinmux.mdwn index 462bc05dc..1d340f226 100644 --- a/docs/pinmux.mdwn +++ b/docs/pinmux.mdwn @@ -100,6 +100,19 @@ but it can also read or control the Core (peripheral). This is its entire purpose: to allow for the detection and triaging of faults. +* Software may be uploaded and run which sets a bit on + one of the peripheral outputs (UART Tx for example). + If the UART TX IO Pad was faulty, no possibility existd + without Boundary Scan to determine if the peripheral + was at fault. With the UART TX pin function being + redirected to a JTAG Shift Register, the results of the + software setting UART Tx may be detected by checking + the appropriate Shift Register bit. +* Likewise, a voltage may be applied to the UART RX Pad, + and the corresponding SR bit checked to see if the + pad is working. If the UART Rx peripheral was faulty + this would not be possible. +