UT_CMD — Commands from two masters, with local / remote

A site often has two masters that both command the same device: the local
panel HMI and a remote SCADA. UT_CMD sits between them and the device:

Each master writes its own variables, and nobody clears them. The block
reacts to each change, so a SCADA that rewrites the same value every poll,
or a value left set, acts only once.
Local / remote: with RemoteEnabled FALSE (a technician on site) remote
requests are refused, counted and reported, except a stop.
Stop wins: a stop and a start in the same scan give the stop.
The outputs are one-scan requests you wire into the device record's cmdXxx
and cmdMode.

Pins

	Pin	Type	Default	What to wire
in	`LocalCmd`	DWORD	0	The local master's command bits (bit 0 stop, bit 1 start … you choose the map). Each bit acts on its rising edge. Wire it (0 if the local master has no command bits)
in	`RemoteCmd`	DWORD	0	The remote master's command bits, same map
in	`LocalMode`	INT	−1	The local master's mode request: acts when it changes to 0 or more. −1 = no request
in	`RemoteMode`	INT	−1	The remote master's mode request
in	`RemoteEnabled`	BOOL	TRUE	FALSE: local control. The remote master is refused (see `remoteStop`). Wire a Local / Remote switch here
out	`Cmd`	DWORD		Accepted command bits, for one scan
out	`Mode`	INT		Accepted mode request for one scan, else −1. Wire into the record's `cmdMode`
out	`Refused`	BOOL		One scan: a remote request was refused
out	`Cmd0` … `Cmd7`	BOOL		Bits 0 to 7 of `Cmd`, for Ladder and FBD. Wire into the record's `cmdStop`, `cmdStart`, `cmdReset` …
inout	`Data`	UT_CMD_DATA		Settings and status

Record `UT_CMD_DATA`

Field	Type	Default	Meaning
`stopMask`	DWORD	16#00000001	The stop / off bits. When one is accepted, every other bit and mode request of that scan is dropped
`localOnlyMask`	DWORD	0	Bits only the local master may give, e.g. a reset that needs someone on site. Refused from remote at all times
`remoteModes`	WORD	16#FFFF	The mode codes the remote master may ask for: bit n = code n. 16#0005 = Off (0) and Auto (2) only. Codes above 15 are refused from remote
`remoteStop`	BOOL	TRUE	Under local control, the remote stop bits and mode 0 (Off) still act. FALSE refuses them too
`lastSource`	UT_CMD_FROM		status: who gave the last accepted request: `UT_FROM_NONE` · `UT_FROM_LOCAL` · `UT_FROM_REMOTE`
`lastCmd`	DWORD		status: its command bits
`lastMode`	INT	−1	status: its mode request (−1 = none)
`refused`	UDINT		status: remote requests refused (not kept over a power cut)
`statusCode`	UT_STATUS		status: see Status codes
`statusText`	STRING(30)		status: `statusCode` in words

How it works

What the masters write.

Command bits: set the bit, and clear it again before the next command (an
HMI momentary button does this: 1 while pressed, 0 when released). A master that
rewrites the same value every poll is fine: only a change from 0 to 1 acts.
Mode: write the code (0 Off, 1 Hand, 2 Auto, 3 OOS, or the device's own
codes). It acts when the value changes. To ask for the same mode again after
someone else changed it, write −1 (or any negative number) first. The block
passes codes 0 and up through; the device checks them.

In each scan:

Each master's new bits (0 → 1) and new mode request are found.
Remote requests are filtered: with RemoteEnabled FALSE only the stopMask
bits and mode 0 pass (and only while remoteStop); localOnlyMask bits and
modes not in remoteModes never pass. A refused request sets Refused for one
scan, adds 1 to refused and is shown in the status.
Stop wins: if a stop bit or mode 0 is accepted, every other bit and any
other mode request in that scan is dropped. Otherwise, when both masters ask for
a mode in the same scan, the local one is used.
Cmd, Cmd0…Cmd7 and Mode carry the result for one scan.

Nothing acts on the first scan after a power cut or PLC start: the block only
reads the masters' values. A command bit or mode left set over a power cut does not
act, so UT_PU_OFF (a mode that comes back Off) can't be undone by a value SCADA
left behind.

Status codes

statusCode is a UT_STATUS (an HMI reads its number); statusText is the same in words.

`statusCode`	`statusText`	When
`UT_ST_LOCAL_REMOTE`	`Local and remote`	`RemoteEnabled` TRUE
`UT_ST_LOCAL`	`Local control`	`RemoteEnabled` FALSE
`UT_ST_REFUSED_LOCAL`	`Refused: local control`	A remote request was refused under local control
`UT_ST_REFUSED_LOCAL_ONLY`	`Refused: local only`	A `localOnlyMask` bit, or a mode not in `remoteModes`

A refusal stays shown until the next accepted request, or until
RemoteEnabled changes.

Using it

Bit map for this pump: bit 0 stop, bit 1 start, bit 2 reset (on site only).

Pump1Cmd(LocalCmd := HMI_P1_Cmd, RemoteCmd := SCADA_P1_Cmd,
         LocalMode := HMI_P1_Mode, RemoteMode := SCADA_P1_Mode,
         RemoteEnabled := NOT LocalSwitch, Data := Pump1CmdData);  (* localOnlyMask := 16#4 *)
Pump1.cmdStop := Pump1Cmd.Cmd0;
Pump1.cmdStart := Pump1Cmd.Cmd1;
Pump1.cmdReset := Pump1Cmd.Cmd2;
Pump1.cmdMode := Pump1Cmd.Mode;

The masters write only HMI_P1_* and SCADA_P1_*, never Pump1.cmd….

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