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#### 9.2.2.11 ACIA module

The ACIA 6551 is an RS232 interface chip. VICE emulates RS232 connections via `/dev/ttyS*` (Unix) or `COM:` (DOS/WIN - not yet?). When saving a snapshot, those connections are of course lost. The state of the ACIA however is restored if possible. I.e. if a connection is already open when restoring the snapshot, this connection is used instead. If no connection is open, a carrier/DTR drop is emulated.

Version numbers: Major 1, Minor 0.

Type | Name | Description
BYTE | TDR | Transmit Data Register
BYTE | RDR | Receiver Data Register
BYTE | SR | Status Register
BYTE | CMD | Command Register
BYTE | CTRL | Ctrl Register
BYTE | INTX | 0 = no data to tx; 1 = Data is being transmitted; 2 = Data is being transmitted while data in TDR waiting to be put to internal transmit register
DWORD | TICKS | Clock ticks till the next TDR empty interrupt