On Sun, 13 May 2001, john/lori wrote: > > I've now almost designed the printed circuit board for the VIC-20 memory > > cartridge. It'll have 4 chips on the top side: Am29LV160D (2MB Flash > > ROM), HM62256B (32kB SRAM), 74LVX245 (data bus buffer), and Lattice 2032 > > programmable logic chip. On the bottom side there are only two 74LVX245 > > chips that buffer the address lines. > > > > It just occured to me, why not use a little bigger pld and > integrate the buffers (and possibly level translation)? (By the way, my friend successfully manufactured one circuit board 2 weeks ago. The components haven't been fitted yet.) We considered using the 100-pin Lattice 2064, but it's a pain to solder, and the circuit board manufacturing tool (a plotter-like thing where the "pens" are drills that chip off copper from the circuit board) cannot make lines or gaps narrower than 200 micrometers. As far as I remember, the pin layout of this 100-pin monster chip is tighter. Using external buffers has another advantage. The address buffers can be mounted on the bottom side, and only the buffered addresses need to be brought to the top side using vias (conducting holes). Marko - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi.
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