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Elite on the BBC Micro

Keyboard: DKS4 [Elite-A, Parasite]

Name: DKS4 [Show more] Type: Subroutine Category: Keyboard Summary: Scan for a particular key press by sending a scan_xin command to the I/O processor
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * TT17 calls DKS4

Arguments: X The internal number of the key to check Returns: A If the key is being pressed, A contains the original key number in X but with bit 7 set (i.e. key number + 128). If the key is not being pressed, A contains the unchanged key number
.DKS4 LDA #&8B \ Send command &8B to the I/O processor: JSR tube_write \ \ =scan_xin(key_number) \ \ which will scan the keyboard for the specified \ internal key number TXA \ Send the parameter to the I/O processor: JSR tube_write \ \ * key_number = X JSR tube_read \ Set A to the response from the I/O processor, which \ will contain the key number with bit 7 set if the key \ is being pressed, or bit 7 clear if it isn't TAX \ Copy the response into X RTS \ Return from the subroutine