Caple C871i Bedienungsanleitung PDF herunterladen (Seite 483)

100

101

Apple II Computer Info

You can't do ANYTHING - it turns off everything in the chip (all

interrupt sources, transmit and receive).

> o You cannot receive if the DCD signal is false.

You also cannot transmit if RTS is turned off.

> CONTROL REGISTER ($C08B + $n0)

> 4 - receiver clock source

> 0 = external receiver clock

Don't use this setting on the SSC - there is no external receiver clock.

> 3210 - internal baud rate generator

> 0 0 0 0 = external receiver clock x 16

Don't use this setting on the SSC - it only works if the ACIA is being

clocked by a square wave input, not a crystal.

> COMMAND REGISTER ($C08A + $n0)

> 32 - transmitter controls (RTS signal)

> 0 0 = transmit IRQ disabled, RTS high

That is "transmitter AND transmit IRQ disabled, RTS high"

> STATUS REGISTER ($C089 + $n0)

> 7 - IRQ pending status

> 0 = no interrupt

> 1 = interrupt has occurred

Be very careful when reading the status register with interrupts

enabled: if the IRQ bit is set, it is cleared by reading this

interrupts but are polling the status register to detect when you can

next transmit a character, you may cause an IRQ to be lost if it

happens to be read by the transmit routine first.

To avoid this, you must check the IRQ flag whenever this register is

read.

This is really only a problem if you're relying on the IRQ

flag to detect an interrupt from the SSC - the interrupt will still

occur, but the interrupt handler will not see the IRQ flag set. If it

is a receive or transmit interrupt, there is a separate flag you can

check, but you cannot identify a state change interrupt for DCD or DSR

unless the IRQ bit is set. You can save the previous state for DCD

and DSR, but a three-way toggle on one of the lines may cause two

interrupts but go undetected.

David Empson

[email protected]

Snail mail: P.O. Box 27-103, Wellington, New Zealand

###################################################### E N D O F F I L E

### ssc.regs

###################################################### E N D O F F I L E

Apple II Computer Technical Information : Apple II Family Hardware Info

ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 483 of 572

1 2 ... 478 479 480 481 482 483 484 485 486 487 488 ... 571 572

Caple C871i Bedienungsanleitung Seite 483

Kommentare zu diesen Handbüchern

Caple C871i Bedienungsanleitung Seite 483

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Kochfelder Caple C871i