This group of signals is responsible for the control of operations between expansion slots. Slave (/SLAVEn) Each slot has its own /SLAVE output, driven actively, all of which go into the collision detect circuitry. The "n" refers to the expansion slot number of the particular /SLAVE signal. Whenever a Zorro II PIC is responding to an address on the bus, it must assert its /SLAVE output within 35ns of /AS asserted. The /SLAVE output must be negated at the end of a cycle within 50ns of /AS negated. Late /SLAVE assertion on a Zorro II bus can result in loss of data setup times and other problems. A late /SLAVE negation for Zorro II cards can cause a collision to be detected on the following cycle. While the Zorro III sloppy cycle logic eliminates this fatal condition, late /SLAVE negation can nonetheless slow system performance unnecessarily. If more than one /SLAVE output occurs for the same address, or if a PIC asserts its /SLAVE output for an address reserved by the local bus, a collision is registered and results in /BERR being asserted. Configuration Chain (/CFGINn, /CFGOUTn) The slot configuration mechanism uses the bus signals /CFGOUTn and /CFGINn, where "n" refers to the expansion slot number. Each slot has its own version of each, which make up the configuration chain between slots. Each subsequent /CFGIN is a result of all previous /CFGOUTs, going from slot 0 to the last slot on the expansion bus. During the AUTOCONFIG process, an unconfigured Zorro PIC responds to the 64K address space starting at $00E80000 if its /CFGIN signal is asserted. All unconfigured PICs start up with /CFGOUT negated. When configured, or told to "shut up," a PIC will assert its /CFGOUT, which results in the /CFGIN of the next slot being asserted. The backplane passes on the state of the previous /CFGOUT to the next /CFGIN for any slot not occupied by a PIC, so there's no need to sequentially populate the expansion bus slots. Data Output Enable (DOE) This signal is used by an expansion card to enable the buffers on the data bus. The main Zorro II use of this line is to keep PICs from driving data on the bus until any other device is completely off the bus and the bus buffers are pointing in the correct direction. This prevents any contention on the data bus.
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