7197 Series II Owner’s Guide Chapter 6: Commands
August 2011
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Printer Firmware Implementation Considerations
The printer firmware will constantly monitor the states listed above. Once the Enable USU
command has been received, from that time forward until the Disable USU command is received,
the printer firmware should transmit a USU message anytime there is a change to a state. When
multiple messages need to be transmitted, there should be a delay of at least 100ms between
messages.
The current state of the USU mechanism Enabled or Disabled should be maintained in the non-
volatile memory. If the printer is reset or power-cycled, and the USU mechanism is in the Enabled
state based on the value in non-volatile memory, the printer should transmit the current status of all
Sensor and State information in the same manner it does in response to a Baseline State Request.
This transmission should be performed once the power-up initialization of the printer has been
completed, and the communications channel has been established.
The purpose of the transmission after power-up is to handle the case of the printer entering an error
state that requires a reset, or power-cycle of the printer to correct it. Unless the current status of
Sensor and State information is transmitted to the host, the controlling software on the host might be
unaware of any changes in status resulting from the reset or power-cycle. The host software would
remain in an error state unless it polled the printer for status information.
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