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Configuration Handbook - Kamami.pl

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Configuring Mercury, APEX 20K (2.5 V), ACEX 1K & FLEX 10K DevicesTable 8–20. Dedicated <strong>Configuration</strong> Pins (Part 4 of 4)Pin NameUserMode<strong>Configuration</strong>SchemePin TypeDescriptionnWS I/O PPA Input Write strobe input. A low-to-high transition causes thedevice to latch a byte of data on the DATA[7..0] pins.In non-PPA schemes, it functions as a user I/O duringconfiguration, which means it is tri-stated.After PPA configuration, nWS is available as a user I/Oand the state of this pin depends on the Dual-PurposePin settings.nRS I/O PPA Input Read strobe input. A low input directs the device to drivethe RDYnBSY signal on the DATA7 pin.If the nRS pin is not used in PPA mode, it should be tiedhigh.In non-PPA schemes, it functions as a user I/O duringconfiguration, which means it is tri-stated.After PPA configuration, nRS is available as a user I/Oand the state of this pin depends on the Dual-PurposePin settings.RDYnBSY I/O PPS and PPA Output Ready output. A high output indicates that the targetdevice is ready to accept another data byte. A low outputindicates that the target device is busy and not ready toreceive another data byte.In PPS and PPA configuration schemes, this pin willdrive out high after power-up, before configuration andafter configuration before entering user-mode.In non-PPS and non-PPA schemes, it functions as a userI/O during configuration, which means it is tri-stated.After PPS and PPA configuration, RDYnBSY is availableas a user I/O and the state of this pin depends on theDual-Purpose Pin settings.nCS/CS I/O PPA Input Chip-select inputs. A low on nCS and a high on CS selectthe target device for configuration. The nCS and CS pinsmust be held active during configuration andinitialization.During the PPA configuration mode, it is only required touse either the nCS or CS pin. Therefore, if only one chipselectinput is used, the other must be tied to the activestate. For exam<strong>pl</strong>e, nCS can be tied to ground while CSis toggled to control configuration.In non-PPA schemes, it functions as a user I/O duringconfiguration, which means it is tri-stated.After PPA configuration, nCS and CS are available as auser I/O pins and the state of these pins depends on theDual-Purpose Pin settings.Altera Corporation 8–67August 2005 <strong>Configuration</strong> <strong>Handbook</strong>, Volume 1

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