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Document the quirks of Symon's ACIA emulation.

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Fixes #7.
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Tim Allen 2023-05-30 23:58:21 +10:00 committed by Seth Morabito
parent 4423623816
commit 4a8a803472
1 changed files with 22 additions and 7 deletions
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README.md
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@ -69,14 +69,29 @@ memory.
![Serial Console](https://github.com/sethm/symon/raw/master/screenshots/console.png)
The main window of the simulator acts as the primary Input/Output
system through a virtual serial terminal. The terminal is attached to
a simulated ACIA, including a programmable baud rate generator that
tries to approximate the correct "feel" of the programmed baud rate.
(The sample Enhanced BASIC ROM image is programmed for 9600 baud)
system through a virtual serial terminal. It also provides CPU status.
Contents of the accumulator, index registers, processor status flags,
disassembly of the instruction register, and stack pointer are all displayed.
It also provides CPU status. Contents of the accumulator, index
registers, processor status flags, disassembly of the instruction
register, and stack pointer are all displayed.
The terminal is attached to a simulated MOS 6551 ACIA. It behaves very much
as described in the datasheet, with some exceptions:
- The simulated ACIA is permanently connected to the virtual terminal,
the Data Carrier Detect and Data Set Ready status bits always indicate
a connection is ready.
- The parity, stop-bits and bits-per-character settings are ignored. The
ACIA always sends and receives 8-bit characters, and parity errors
do not occur.
- The ACIA tries to honour the configured baud rate, but as a special case
the default "16x External Clock" rate is interpreted to mean "as fast as
possible" (The sample Enhanced BASIC ROM image is programmed for 9600 baud).
- The ACIA ignores the configured state of the Data Terminal Ready pin;
it is always ready to receive and transmit.
For more information on the MOS 6551 ACIA and its programming model,
see the official datasheet:
- [MOS 6551 ACIA](http://archive.6502.org/datasheets/mos_6551_acia.pdf)
![Font Selection](https://github.com/sethm/symon/raw/master/screenshots/font_selection.png)