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Notes and copy/paste error (nw)

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This commit is contained in:
Vas Crabb 2015-10-30 16:46:21 +11:00
parent ce1e6e6306
commit 15e68a47d9
1 changed files with 16 additions and 2 deletions
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18
src/mame/drivers/osborne1.c
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@ -40,8 +40,22 @@ used, and the value on the data bus is completley ignored.
Selecting between bank 1 and bank 2 is also affected by M1 and IRQACK
conditions using a set of three flipflops.
The serial speed configuration implements wiring changes recommended in the
Osborne 1 Technical Manual. There's no way for software to read the
selected baud rates, so it will always call the low speed "300" and the high
speed "1200". You as the user have to keep this in mind using the system.
Serial communications can be flaky when 600/2400 is selected. This is not a
bug in MAME. I've checked and double-checked the schematics to confirm it's
an original bug. The division ratio from the master clock to the baud rates
in this mode is effectively 16*24*64 or 16*24*16 giving actual data rates of
650 baud or 2600 baud, about 8.3% too fast (16*26*64 and 16*26*16 would give
the correct rates). MAME's bitbanger seems to be able to accept the ACIA
output at this rate, but the ACIA screws up when consuming data from MAME's
bitbanger.
TODO:
- Implement serial port
- Verify frequency of the beep/audio alarm.
***************************************************************************/
@ -170,7 +184,7 @@ static INPUT_PORTS_START( osborne1 )
PORT_START("CNF")
PORT_CONFNAME(0x06, 0x00, "Serial Speed")
PORT_CONFSETTING(0x00, "300/1200")
PORT_CONFSETTING(0x02, "600/1200")
PORT_CONFSETTING(0x02, "600/2400")
PORT_CONFSETTING(0x04, "1200/4800")
PORT_CONFSETTING(0x06, "2400/9600")
PORT_CONFNAME(0x01, 0x00, "Video Output")