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+## Overview
+
+The `UCD90320Monitor' class determines its device configuration from a JSON
+configuration file. The configuration file describes the power sequencer rails
+and power good (pgood) pins defined in the system.
+
+## File Name
+
+The expected filename format is `UCD90320Monitor_<systemType>.json`, where
+`<systemType>` is a `Compatible System` name from a `Chassis` Entity Manager
+configuration file.
+
+Example file name:
+```
+UCD90320Monitor_mysystem.json
+```
+
+## File Format
+
+The configuration consists of an array of `rails` and an array of `pins`. Both
+`rails` and `pins` use a `name` element. The name element should be mnemonic
+and unique. If the BMC system utilizes the openpower-pels extension, then it
+will be used as an index into the `phosphor-logging` Message Registry.
+
+Example 'rails' array with 'name' elements:
+```
+"rails": [
+    { "name": "12.0V" },
+    { "name": "VDN_DCM0" }
+]
+```
+
+The `pins` array also uses a `line` element which is the GPIO line number
+of the pgood pin in the power sequencer device.
+
+Example 'pins' array with 'name' and 'line' elements:
+```
+"pins": [
+    {
+        "name": "5.0V",
+        "line": 67
+    },
+    {
+        "name": "VCS_DCM0",
+        "line": 74
+    }
+]
+```
+
+Both `rails` and `pins` can optionally define a `presence` element which is an
+inventory path to a system component which must be present in order for the rail
+or pin to be used in failure isolation. By default, a rail or pin is considered
+to be present, which could mean the necessary parts are always present in the
+system or that a not present part would not cause a pgood failure.
+
+Example 'rails' array element including 'presence' element:
+```
+{
+    "name": "VCS1",
+    "presence": "/xyz/openbmc_project/inventory/system/chassis/motherboard/vrm1"
+}
+```
+
+Example 'pins' array element including 'presence' element:
+```
+{
+    "name": "VPCIE",
+    "line": 61,
+    "presence": "/xyz/openbmc_project/inventory/system/chassis/motherboard/vrm0"
+}
+```