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comparison venus/doc/Flash+RAM @ 90:e8ce3b688723

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venus/doc/Flash+RAM: R372 addition documented
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 10 Dec 2021 23:00:44 +0000
parents 09cda55086b1
children
comparison
equal deleted inserted replaced
89:30f567edd2b6 90:e8ce3b688723
80 MCP would not be acceptable. However, in the case of FC Venus, our core 80 MCP would not be acceptable. However, in the case of FC Venus, our core
81 shieldcan section already includes many additions beyond Leonardo/TR-800: 81 shieldcan section already includes many additions beyond Leonardo/TR-800:
82 consider U401 through U404, all of which need to go into this expanded core 82 consider U401 through U404, all of which need to go into this expanded core
83 section. Thus if we are already expanding the core for other reasons, we should 83 section. Thus if we are already expanding the core for other reasons, we should
84 be able to throw in this flash+RAM MCP expansion as well. 84 be able to throw in this flash+RAM MCP expansion as well.
85
86 Reset circuit population option
87 ===============================
88
89 If U303 is populated and R372 is unpopulated (necessary for S71PL129N MCP, the
90 current plan for initial board build), the flash reset signal will be fed with
91 ON_nOFF, translated to 2.8V via U303. However, if the populated MCP is S71PL-J,
92 then there are two options:
93
94 * Flash reset may be generated "in the new way" like for S71PL129N, with U303
95 populated and R372 unpopulated.
96
97 * If U303 is omitted and a 0R jumper is populated at R372 instead, the circuit
98 reverts to TI's old way of using Calypso FDP for flash reset.
99
100 The unpopulated R372 footprint will also serve as a pair of test points for
101 oscilloscope probing, allowing both Calypso FDP output and the actually-used
102 output of U303 to be observed.