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Chapter 4 Theory of Operation

4.2 Address Selection

Address lines A15 to A5 and address modifier lines AM5 to AM0 are compared (by U60 and U66) with the setting of the switches S1 to S3, and the jumper block JB1. When a match is found and the address strobe is active the board select signal (/bs) is generated. The pal U61 decides, depending on the value of A4, if either the BIM or one of the channel registers is selected. The channel register select signals are distributed to one of the four channels by U47 and U54, depending on the values of A2 and A3. The board responds on odd and even byte addresses but only on odd addresses relevant data is transferred.

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