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BASIC IV ROM Routines
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BF66 Detect Tube presence

Submitted by Steve Fewell

Description:

Call OSBYTE &EA with Y = #&FF to detect Tube presence.
Transfer the result to A, which will contain the following on return:
      0 - If no Tube is present       255 - If Tube is present


Disassembly for the Detect Tube presence routine

BF66

 

169 234

A9 EA

LDA#&EA

BF68

 

162 000

A2 00

LDX#&00

BF6A

 

160 255

A0 FF

LDY#&FF

BF6C

 

032 244 255

20 F4 FF

JSR &FFF4   OSBYTE

BF6F

 

138

8A

TXA

BF70

`

96

60

RTS

 


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