Specifications

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XON "n" Default: $11 <CTRL-Q>
Mode: All Host: XN
_________________________________ Parameters: __________________________________
"n" - 0 to $7F (0 to 127 decimal) specifies an ASCII character code.
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XON selects the PK-900 Start character that is sent to the computer or
terminal to restart input from that device.
The Start character default value is <CTRL-Q> for computer data transfers.
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ZFree Immediate Command
Mode: All Host: ZF
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This command is primarily of interest to HOST mode programmers. ZFREE is an
immediate read-only command that returns the amount of data RAM that is
available in the PK-900. n is the number of free internal memory blocks.
Each memory block holds 28 bytes of data.
Use the ZFREE command to avoid the situation in which a host mode application
sends a block of data to be transmitted, but the controller cannot issue a data
acknowledgement (5F X X 00) to the host computer right away because the TNC is
too full. The application should not send data to the controller if it would
cause the value of ZFREE to drop below 64. To avoid the transmission of RNR
(device busy) packets, the application should make sure ZFREE does not drop
below 128.
Note that ZFREE is different from the FREE command, which shows the number of
message bytes available to the maildrop. (ZFREE times 28 is always larger than
the value of FREE.)
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