Konference: SAPI-1 a československé mikropočítače

Od: melsoft
Datum: 20.9.2010 15:17
Předmět: Re: Re: Re: Re: Tiskárna v CP/M

Re: Re: Re: Re: Tiskárna v CP/M:

Ještě jsem našel tohle:
In the polled mode of printing, the character bits are put on the DATA lines,
 BUSY is tested repeatedly until it is found to be low, then the ~STROBE pulse
is sent. The printer sets BUSY high when the character data have been latched
and sets it low again when the character has been processed. (The Centronics
protocol specifies that the DATA lines be stable from at least 500 ns before to 
at least 500 ns after the ~STROBE pulse, and the ~STROBE pulse be at least 500
ns long. These times may of course be shortened for a specific printer, at the
risk of loss of generality.) Programs using the polled mode should include a
"timeout"  counter to guard against a permanent BUSY condition. BIOS calls and
DOS functions use this mode for printing.

Potvrzuje to moji domněnku s inicializací /STROBE a v podstatě i to zapsání
dat přímo do portu tiskárny (bez nutnosti úschovy v C). Kolik NOPů musím
dát na 500ns? To je jeden takt procesoru ne?

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