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This card does not have its own ports. It must use the
host machine's. In general these will behave exactly as the equivalent
ports on a normal PC, but in a few instances it is possible for the hosted
nature of the ports to cause different behaviour. Timing-critical devices
using interrupts may find that the increased interrupt latency is a problem,
and serial performance may not be as fast as expected.
In practice, parallel port devices such as network adaptors, sound adaptors, IDE interfaces can be expected to work, and serial devices at speeds of up to 28,800bps. To use the host serial or parallel port you must specify these options
in !PCConfig. See Printing on page 19 and Serial
port on page 20 for details.
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The Aleph One PC Expansion cards are equipped with their
own serial and parallel interfaces. These interfaces behave exactly like
the first serial port (COM1) and parallel port (LPT1) on a PC.
You can send and receive data over both interfaces, allowing dongles and modems to be used straightforwardly. Be sure to select Single-tasking (full-screen) mode when using the serial or parallel interfaces to achieve reliable operation. In multi-tasking mode it is possible for other RISC OS applications to interfere with the PC application and cause errors. |
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It is possible to fit a second serial port and enhanced
serial/parallel controller to expansion cards. The enhanced parallel port
allows greater throughput with parallel port devices, and the enhanced
serial port is buffered for improved high-speed comms.
The second serial port will appear to PC software as COM2. This port uses interrupt three, so you need to change the interrupt used by the mouse from its default of 3. You will need to use the Advanced configuration dialogue, and possibly to edit the !PCconfig file ConfData (see A.2 Enabling advanced configuration options on page 73), and change the BUSMouseInt setting (see Interrupt number for bus mouse on page 80).
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| Normally !PC will find and use the host computer’s floppy
drive without you doing anything. Drive 0 will appear to the PC as drive
A: and drive 1 (if present) will appear as PC drive B:.
If you have a non-standard size drive, or have added external drives
(for example 5.25"), it is possible that !PC will fail to identify the
size or density of the drive correctly. In this case you must use the Floppy
option in the !PC config file to specify the drive capacity.
(See Floppy drive size on page 80).
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| Because the floppy disk drive is hosted, and has a different
floppy >controller to a ‘real PC’, software which tries to use
the floppy controller directly will not work. This means that floppy protection
schemes involving strangely formatted sectors will not work, and neither
will backup applications. This includes MSBackup, Fastback, Norton Backup,
and PCTools Backup, which all require direct floppy control.
We recommend that you use PKZIP v2 for floppy backup instead. Other programs that attempt to access the floppy hardware directly are operating systems other than DOS/Windows, such as OS/2, Linux, and Windows NT. |
| If your Acorn computer is equipped with a built-in high-density
disc drive (eg A5000 and Risc PC) you can format, read and write high-density
(1.44MB) DOS discs directly. Other models of Acorn computers can neither
read nor write such discs without a hardware upgrade.
Suitable upgrades that have been tested are high density drives from Beebug/RISC developments and The Serial Port/Arxe. |
| Aleph One Ltd. | 56-58 |
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