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ZX Interface 1: Difference between revisions
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* When a drive is selected, it starts running automatically, and in the absence of "write" and "erase" signals, will start returning data to the Interface1, allowing it to detect gaps and syncronisation pulses. If it is not deselected, it will continue to run indefinitely, until power is removed. It is possible to turn on more than one drive at a time, which would result in a bus conflict and may damage the drives, so only one drive should ever be selected when accessing the registers directly from code. | * When a drive is selected, it starts running automatically, and in the absence of "write" and "erase" signals, will start returning data to the Interface1, allowing it to detect gaps and syncronisation pulses. If it is not deselected, it will continue to run indefinitely, until power is removed. It is possible to turn on more than one drive at a time, which would result in a bus conflict and may damage the drives, so only one drive should ever be selected when accessing the registers directly from code. | ||
* ''Comms Data'' is used to select which microdrive is selected. It's an 8 bit word, with a single bit set. The first bit in the sequence is Drive 8, the last one is Drive 1. | |||
* ''Comms Clock'' clocks the drive selection data through the chain of microdrives. | |||
* When ''Erase'' is '''reset''' the tape is erased. Typically turns on 2ms before writing, and although it turns off with the end of write, takes around 2ms to stop erasing. | * When ''Erase'' is '''reset''' the tape is erased. Typically turns on 2ms before writing, and although it turns off with the end of write, takes around 2ms to stop erasing. | ||
* ''R/W'' instructs the microdrive to read or write. When ''R/W'' is '''set''' the data channel reads, when '''reset''' the data channel writes. Used in conjunction with ERASE. | * ''R/W'' instructs the microdrive to read or write. When ''R/W'' is '''set''' the data channel reads, when '''reset''' the data channel writes. Used in conjunction with ERASE. | ||
* ''Write Protect'' indicates that a cartridge is write protected. If a drive that is not connected is accessed, it will be in "protect" by default to prevent format commands from working. | * ''Write Protect'' indicates that a cartridge is write protected. If a drive that is not connected is accessed, it will be in "protect" by default to prevent format commands from working. | ||
* ''Gap'' and ''Sync'' are used to locate the correct block of data on the microdrive. They are produced by the ULA which decodes the synchronisation pulses and detects the gaps in between sectors and between the sector file and the record file. | * ''Gap'' and ''Sync'' are used to locate the correct block of data on the microdrive. They are produced by the ULA which decodes the synchronisation pulses and detects the gaps in between sectors and between the sector file and the record file. | ||