| ??? 02/01/08 07:34 Read: times |
#150144 - it isn't that simple. Responding to: ???'s previous message |
Jan Waclawek said:
Richard Erlacher said:
In this case, I want 7-bit ASCII output in parallel, strobed, data format. It only requires that one substitute a 5-6 line routine for a 25 line one that talks to the I2C hardware. It seems to me that a little 20-pin part could handle this just fine, or, for that matter, a 16-pin part. Get the 8042 - it's ready to use. You just need to excavate it from an old PC motherboard, from the '286/'386 era. Probably not without some more logic. Look at how the thing works. It's a bus-oriented peripheral. The application is just a parallel input port, and I only have access to the port pins. IMHO you can rip off some 20 unimportant pins if it makes you nervous that it is DIP40... :-)
JW It doesn't make me nervous that it's a 40-pin device. It makes me unhappy that it doesn't fit. It needs to be a 20-pin device, because there's a 20-pin DIP socket into which it has to fit. Aside from that, it would require additional logic to make the 8042 work. That guy requires that you provide a select strobe a read tag, and a pair of addresses. It's possible, since it's DMA capable, that it requires more, and the application is already designed and funcitonal. It just needs a new MCU. The original was designed for the MC68HC705J1. I can't get those, or any other 20-pin family member. I have 40-pin DIP MC68HC705C8 types in considerable quantity (2-3 rails). They'll do what I want, but they won't fit. Now, nothing's ruled out, but I want a small package and I want it to fit. RE |
