S4 emulation of 512Kx8 3v3 EPROM

[Guest]

Does anyone know if the dataman S4 will emulate a 3v3 512kx8 EPROM (like ST27LV401)? anyone have any experience of this (512k or 3v3 emulation)?

Cheers
Simon Fisher
Swansea UK

[Dataman (Neil Parker)]

Hi Simon,

S4 cannot emulate 3.3V devices. This is not a limitation of S4 itself - it can read 3.3V devices due to its 74HCT inputs - The problem is that when S4 sends data to host equipment, then 74HCT outputs give voltage levels close to 5V which can damage your hardware if it is not 5V tolerant.

Regards,

Neil

[Guest]

Thanks for that Neil.

Do you think it would be OK to use pull down resistors (say 3k3) in the data lines with series resistors (say 1k8) in those lines? The data line outputs from the dataman would then be at 3v3 into my micro, as you say the address, OE, CS etc. lines would be output from my micro at 3v3 and would be read OK by the dataman.

Cheers
Simon Fisher

[Dataman (Neil Parker)]

Hi again Simon,

Electrically this is okay, but sadly it probably will not work. The reason is capacitance which causes time delays. A 1K8 resistor is quite large so if you think about say 50pf parasitic capacitance then the delay = 1800 * 50E-12=9E-8s, which is 90ns added to S4 RAM access and that would prohibit using emulation. You can experiment with lower value resistors just take care not to damage drivers from an excessive current. We cannot be held responsible for any damage that occurs from trying this.

Hope this gives you more insight.

Neil