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Don't assert OE and CS simultaneously during electrical test

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If you do, and a SIMM is installed in the socket, you will get an
erroneous short detected for any data pins that are currently outputting
a 0. Avoid this by testing OE and CS for 5V shorts separately.
This commit is contained in:
Doug Brown 2023-08-06 20:35:30 -07:00 committed by Doug Brown
parent 0b88f61542
commit c46b9d5e5f
1 changed files with 19 additions and 4 deletions
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23
tests/simm_electrical_test.c
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@ -214,8 +214,12 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t))
ParallelBus_SetDataPulldowns(SIMM_DATA_PINS_MASK);
ParallelBus_SetCSPullup(false);
ParallelBus_SetCSPulldown(true);
ParallelBus_SetOEPullup(false);
ParallelBus_SetOEPulldown(true);
// We can't enable pulldowns on both CS and OE simultaneously, because if
// they're both low at the same time, a SIMM mounted in the socket will
// output data and interfere with our electrical test. So only enable CS's
// pulldown at first. Enable a pullup on OE just to be sure it's not low.
ParallelBus_SetOEPullup(true);
ParallelBus_SetOEPulldown(false);
ParallelBus_SetWEPullup(false);
ParallelBus_SetWEPulldown(true);
@ -277,6 +281,17 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t))
}
curPin++;
// Now that we've tested CS, turn off its pulldown and turn on OE's pulldown instead.
// Pull up CS -- again, this ensures that a SIMM won't output data and interfere with
// the electrical test if it's mounted in the socket right now.
ParallelBus_SetOEPullup(false);
ParallelBus_SetCSPulldown(false);
ParallelBus_SetOEPulldown(true);
ParallelBus_SetCSPullup(true);
// Wait a brief moment...
DelayMS(DELAY_SETTLE_TIME_MS);
// Output enable...
if (ParallelBus_ReadOE())
{
@ -299,8 +314,8 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t))
}
curPin++; // Doesn't need to be here, but for consistency I'm leaving it.
// Clear the pulldowns now that we're done; we won't need them anymore
// for the rest of the testing
// Clear the pulldowns now that we're done with 5V short testing; we won't
// need them anymore for the rest of the electrical test.
ParallelBus_SetAddressPulldowns(0);
ParallelBus_SetDataPulldowns(0);
ParallelBus_SetCSPulldown(false);