<li>When there's an active TCP connection, then the 6551's Status register has DCD,DSR bits clear (active low), and DIPSW2 has CTS bit clear (active low). When there's no TCP connection, then all these bits are set (inactive).
<li>The TCP mode can expose buggy Rx interrupt handling code where the 6551's Status register is read more than once in the Interrupt Service Routine (ISR).
<li>Details: TCP mode doesn't throttle the serial data-rate, so after reading the Status register (to clear the Rx interrupt) the Rx interrupt may get asserted immediately if there is more data in the TCP receive buffer, resulting in a missed interrupt (and therefore missed Rx data).
<li>The 6551's Command register's DSR (bit0) must be set, to enable interrupts (Rx, Tx) along with the respective Rx and/or Tx bits (bit3:1). This is part of the 6551 specification, but (DSR bit) has only been enforced by AppleWin since 1.27.4.
<li>NMOS 6551 ACIA CTS bug: transmission of an already-started frame will stop immediately when CTS is taken false, the byte will be lost, and the TxD line will go to marking.
<ul>
<li>NB. The CMOS 6551's will finish the frame, so assume that AppleWin emulates a CMOS 6551.
</ul>
<li>AppleWin's 6502/65C02 emulation doesn't emulate the false read for STA $C088,X (where X=$20).
<ul>
<li>Don't do this to write to the 6551's Transmit register.
<li>On AppleWin this is fine, but on real hardware (in full duplex mode) you may falsely read (and clear) the 6551's Receive register.
<li>Instead (like the SSC's firmware) do this: STA $BFFF,Y (where Y=$A9).
</ul>
</ul>
<br>
<br>
<h4>Using TCP mode with the Apple // Game Server:</h4>
The TCP interface to the SSC can be used by the <ahref="https://sourceforge.net/projects/a2gameserver">Apple // Game Server</a> (AGS).<br>
For details see the notes that comes with AGS, but in summary:<br>
<ul>
<li>Boot the Apple II to AppleSoft (ie. power on and hit Ctrl-Reset) and type IN#2.
<li>From a Windows DOS box, start AGS with "localhost 1977 apple2e". This will boot the emulated Apple II from AGS.
<li>Nb. Only Enhanced Apple //e is working at the moment.