Wanted: ASM-48 for Intellec MDS-2

On Tue, May 19, 2015 at 11:28 PM, Mike Stein <mhs.stein at gmail.com> wrote: "Normal operation" is the key phrase. ROM (or EPROM) verification mode is not considered "normal operation". In normal operation, the 8041A/8641A/8741A is executing the ROM/EPROM code, and you can apply an address externally to the port pins until the cows come home, but that won't make it dump the contents of that address. This isn't a 2716. There isn't a "read (normal)" mode. Normal mode is executing code, and doesn't allow reading the ROM (or EPROM) contents externally. Verification mode is the only mode that provides for external access to the ROM/EPROM contents. The only documented way the chip knows to be in verification mode is a supervoltage on the EA pin. A National Semiconductor app note suggests that 9V is adequate for reading their 804x masked ROM parts; they specifically mention internal circuitry that detects a voltage on EA above a certain threshold which puts the part into verification mode. The 9V National describes might or might not be adequate to read Intel masked ROM parts. Intel specified 12V to read the 8048. Intel neglected to specify the supervoltage required for ROM verification mode for the 8041 and 8041A, but I'm pretty sure they expected 12V for those as well.