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Routines |
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Used by the routines at SAVE_ETC, SA_CONTRL, PO_SCR, CLS, CL_ALL, ED_EDIT, ED_UP, MAIN_EXEC, LIST, LPRINT, STR_ALTER, INPUT, str and read_in.
This subroutine is called with the A register holding a valid stream number - normally +FD to +03. Then depending on the stream data a particular channel will be made the current channel.
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CHAN_OPEN | 1601 | ADD A,A | The value in the A register is doubled and then increased by +16. | |||||||
1602 | ADD A,$16 | |||||||||
1604 | LD L,A | The result is moved to L. | ||||||||
1605 | LD H,$5C | The address 5C16 is the base address for stream +00. | ||||||||
1607 | LD E,(HL) | Fetch the first two bytes of the required stream's data. | ||||||||
1608 | INC HL | |||||||||
1609 | LD D,(HL) | |||||||||
160A | LD A,D | Give an error if both bytes are zero; otherwise jump forward. | ||||||||
160B | OR E | |||||||||
160C | JR NZ,CHAN_OP_1 | |||||||||
This entry point is used by the routine at STR_ALTER.
Report O - Invalid stream.
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REPORT_O | 160E | RST $08 | Call the error handling routine. | |||||||
160F | DEFB $17 | |||||||||
Using the stream data now find the base address of the channel information associated with that stream.
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CHAN_OP_1 | 1610 | DEC DE | Reduce the stream data. | |||||||
1611 | LD HL,($5C4F) | The base address of the whole channel information area (CHANS). | ||||||||
1614 | ADD HL,DE | Form the required address in this area. | ||||||||
This routine continues into CHAN_FLAG.
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