Skip to navigation


Drawing the screen: WSCAN

[Elite-A, Parasite]

Name: WSCAN [Show more] Type: Subroutine Category: Drawing the screen Summary: Wait for the vertical sync by sending a sync_in command to the I/O processor
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * check_keys calls WSCAN * DELAY calls WSCAN * DK4 calls WSCAN * DK4_FLIGHT calls WSCAN * TT102 calls WSCAN
.WSCAN LDA #&85 \ Send command &86 to the I/O processor: JSR tube_write \ \ =sync_in() \ \ which will wait until the vertical sync before \ returning control to the parasite JMP tube_read \ Set A to the response from the I/O processor, which \ will be sent when the vertical sync occurs (it doesn't \ matter what the value is), and return from the \ subroutine using a tail call