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--- mfiio [2009/03/06 07:10]
twdorris created
+++ mfiio [2024/03/15 11:16] (current)
@@ Line 1: / Line 1: @@
 ====== MFI Schematic - I/O ======
-You can tell from the MFI schematic in the shop manual which pins are inputs and which pins are outputs from the ECU.  This page explains how.
+This page is a collection of notes on how to read certain information off the MFI schematic in the DSM shop manual.  First, reference the [[https://www.ecmtuning.com/images/forums/2GECUMFI.pdf|2G MFI schematic]] (or the [[https://www.ecmtuning.com/images/forums/1GECUMFI.pdf|1G MFI schematic]]) for an example of what this schematic looks like.
-First, reference the [[http://www.dsmlink.com/images/forums/2GECUMFI.pdf|2G MFI schematic]] (or the [[http://www.dsmlink.com/images/forums/1GECUMFI.pdf|1G MFI schematic]]) for an example of what this schematic looks like in the Mitsubishi shop manual.  The following is a clip from the 2G manual showing three connections between the ECU and the Automatic Transmission computer (TCU).
+===== ECU Pins =====
-{{http://www.ecmtuning.com/images/forums/atinput.gif}}
-Look at pins 43 and 46 on the ECU side.  You'll see a +5v pull up resistor on each input.  That means, when nothing is connected to that input (or when the TCU output is "inactive"), the ECU's sense circuit will "see" 5v.  Which means in order for the AT to "active" that input, it will need to switch the input to ground (which is what the transistor with a connection to ground illustrates on the TCU side).
-This all clearly indicates that these pins are "inputs" to the ECU that the TCU is driving as "outputs".  So some function inside the TCU will request some function to be activated inside the ECU by pulling those inputs to ground.
-And if you'll notice, the two circuits are reversed on ECU pin 7 (AT pin 17), which tells us that that particular connection is an output from the ECU that controls some function inside the AT computer.
+==== Input - analog ====
+{{https://www.ecmtuning.com/images/forums/ecudocs/input-analog.gif  }}
+This is a simple analog (0-5v) input to the ECU.  No significant load on the sensor is illustrated in this diagram.  When nothing is connected to this input, the ECU will see an undefined value.  It could be just about anything from 0-5v.
+==== Input - analog w/pull down ====
+{{https://www.ecmtuning.com/images/forums/ecudocs/input-analog-pulldown.gif  }}
+This is a 0-5v input to the ECU but with a pull down through some resistor.  The implication here is that any voltage source (sensor) connected to this input will be expected to drive the load of that pull down.  Some sensors simply can not do this.  You can get more info on our [[ecuinputdata|ECU Input Data]] page.
+When nothing is connected to this input, the ECU is going to "see" ground (0v).
+==== Input - analog w/pull up ====
+{{https://www.ecmtuning.com/images/forums/ecudocs/input-analog-pullup.gif  }}
+This is a 0-5v input to the ECU but with a pull up to 5v through some resistor.  Which means when nothing is connected to this analog input, the ECU is going to "see" +5v.
+==== Input - analog w/pull up & down ====
+{{https://www.ecmtuning.com/images/forums/ecudocs/input-analog-pullupdown.gif  }}
+This is a 0-5v input to the ECU but with a pull down to ground **and** a pull up to +5v through some resistor combination.  The implication here is that any voltage source (sensor) connected to this input will be expected to drive the load of that pull down.  Some sensors simply can not do this.  You can get more info on our [[ecuinputdata|ECU Input Data]] page.
+An example of this type of input would be a temperature sensor.  Thermistors require this type of drive circuit.
+==== Input - digital ====
+{{https://www.ecmtuning.com/images/forums/ecudocs/input-digital.gif  }}
+This is a digital input to the ECU.  The default "value" seen by the ECU for this input is +5v (when nothing is connected to the input or when the device connected to that input is simply "inactive").  When the input is "active", the external device is expected to pull this signal to ground, which will cause the ECU to no longer see the +5v value and instead see ground reference through the transistor.
+==== Output - digital ====
+{{https://www.ecmtuning.com/images/forums/ecudocs/output-digital.gif  }}
+This is a digital output from the ECU.  When it's "active", the output will be switched to ground (low-current sensor ground!).  When the output is "inactive", it will be connected to nothing (floating).

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