# HG changeset patch # User Mychaela Falconia # Date 1639177244 0 # Node ID e8ce3b688723ad07615938e72e0ab347df7aeb1c # Parent 30f567edd2b661d5da1fd192af78c9ecd3ae1bac venus/doc/Flash+RAM: R372 addition documented diff -r 30f567edd2b6 -r e8ce3b688723 venus/doc/Flash+RAM --- a/venus/doc/Flash+RAM Fri Dec 10 22:40:08 2021 +0000 +++ b/venus/doc/Flash+RAM Fri Dec 10 23:00:44 2021 +0000 @@ -82,3 +82,21 @@ consider U401 through U404, all of which need to go into this expanded core section. Thus if we are already expanding the core for other reasons, we should be able to throw in this flash+RAM MCP expansion as well. + +Reset circuit population option +=============================== + +If U303 is populated and R372 is unpopulated (necessary for S71PL129N MCP, the +current plan for initial board build), the flash reset signal will be fed with +ON_nOFF, translated to 2.8V via U303. However, if the populated MCP is S71PL-J, +then there are two options: + +* Flash reset may be generated "in the new way" like for S71PL129N, with U303 + populated and R372 unpopulated. + +* If U303 is omitted and a 0R jumper is populated at R372 instead, the circuit + reverts to TI's old way of using Calypso FDP for flash reset. + +The unpopulated R372 footprint will also serve as a pair of test points for +oscilloscope probing, allowing both Calypso FDP output and the actually-used +output of U303 to be observed.