TECHNICAL NOTES
- RT2
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TECHNICAL NOTES
- RT2
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A DIP switch on the RMS4137-1 Interface Module is used to enable or disable the External Control Panel (ECP); however, access to this switch may be difficult. For this reason, a command is available to allow the host computer to directly make this selection. The operation of the system regarding the status of the ECP is explained in this document; the state diagram in Figure 1 helps to illustrate this operation.
After power-up or reset, the status of DIP switch SW1-1 on RMS4137-1 is read, and stored in memory. If this switch is open (or the interface module is not installed), the system will assume the ECP is not present; this corresponds to the mode of operation of State I (Figure 1), in which host computer commands to enable or disable the ECP are ignored.
If SW1-1 is closed, the system will know that the RMS4137-1 Interface Module is installed, and will allow an external host computer to enable or disable the ECP. Initially, the system defaults to an enabled state (State II), and determines channels to be scanned from the status read from the switches on the ECP. (Recall that if a sampling rate of 25 samples/sec has been selected, all channels will be scanned, regardless of the on/off status of the switches).
Operation in State II is the same as before, with the exception that now a command to disable the ECP may be issued by the host computer; this will take the Recorder to State III, which corresponds to the "automatic" mode of operation. In this state the system ignores all selections made through the ECP, and full control of the unit is in hands of the host computer and/or the recorder's control panel.
The host computer may return the recorder from State III back into State II, by issuing the appropriate command. If no change in sampling rate took place while in State III, the unit will simply return to State II and determine the channel on/off status from current switch positions in the ECP. If a change in the sampling rate took place, it must be remembered that for fixed sampling rates (25, 50, 100, or 200 samples/sec) only those channels turned 'on' at the time of this selection will be scanned.
The command to enable/disable the ECP has the following syntax:
[ 6DH, X ] ,
where 6DH is the command itself, and X is a single-byte argument such that:
X = 00H ---- disables the ECP
X = 01H ---- enables the ECP
Making use of the features described, the system may operate in a "back-up" mode, as follows:
a) SW1-1 on RMS4137-1 should be closed to indicate the ECP is present.
b) After power-up or reset, the unit will default to State II, allowing manual operation of the system.
c) The host computer will initiate communications with the recorder, putting it on-line, and will then send the command to disable the ECP.
d) The recorder enters State III, allowing automatic operation of the system. The host computer will send commands to set-up the recorder's configuration, and will initiate recording as required by the application.
e) Normally, the system will continue to operate in automatic mode until the end of the exercise. Should the host computer crash, a reset of the recorder will revert it back to manual mode (State II).
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