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'z16' command (timing for fast emulation mode)
This command has two parameters (min. and max) and is only used for fast emulation mode.
min = min gap time between messages (ms), default 20ms.
This time is used by the metal detector, if a
change to the screen message was detected.
max = max gap time between messages (ms), default 1000ms.
This time is used if there was no change to the screen message.
The timings should only be changed whilst fast emulation mode is not active. All times are approximate, typically the
actual delay will be value + 8 ms.
Note: In most instances there should be no need to alter the default values.
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'z20' command
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The 'z20' cmd transmits the information to update the screen. This command behaves slightly different
depending on the emulation mode used (fast or normal).
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In both modes (fast and normal emulation) the screen info data transmitted is packed as described under
'Screen package format'.
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The 'z20' command in normal emulation mode
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The command behaves like any other command under the PCI protocol.
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The screen update has to be requested by the host.
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The message format would look as follows:
(STX)G(VALUE)M(VALUE)z20,(ENCODED DATAPACK)(ETX)(CRC)
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The 'z20' command in fast emulation mode
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The 'z20' cmd is automatically transmitted on a timed interval.(For timing see 'z16' cmd)
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The host processor must not respond with ACK/NAK's for the 'z20' cmd.
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The 'z20' message is 'injected' into the normal protocol data regardless if the serial link is
•
busy or not.
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The start and end chars are different:
(First char: 'SOH' 0x01 / End char: 'EOT' 0x04)
This has been done to give the host the ability to filter out the screen update information from the normal
protocol. The host has to scrutinize every character received for a potential 'SOH' character and, if
detected, remove the screen up-date info from the normal protocol stream.
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The message format would look as follows:
(SOH)z20,(ENCODED DATAPACK)(EOT)(CRC)
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APPENDIX D
4618-021
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