FRAM71 for HP-71B, short update #3
Message #1 Posted by Hans Brueggemann on 6 Jan 2013, 1:24 p.m.
this is to let you know that work on the FRAM71 is still in progress.
currently at HW revision 102, it will have to go through one more revision to remove a Particular Extra Connection, Hand-wired (PECH) from the final layout.
Sum-up of actual feature-set:
1) Up to seven ports of configurable FRAM (Ports 5.0 to 5.06)
2) RAM size individually configurable for each port from 1kByte to 64 kByte
3) Configuration is done by POKE "2C000", "CONFWORD"
4) Additional fixed 64 kByte FRAM hard-wired at 0x0000-0x1FFFF, activated and protected by jumpers
5) Port(5.0) can be re-declared from soft-configurable RAM to hard-configured ROM at 0xE0000 by jumper, without losing its contents (you get the idea, and yes, that works!)
unfortunately, the card reader bay doesn't have access to the internal OD line of the HP-71B. in order to use feature 4), you will need some kind of "dummy module" plugged into Port(3) that activates the OD line. however, FRAM71 will have a provision to optionally assert OD=1 to the HALT signal of the card reader bay, which can be re-directed to the OD-line by a small hardware modification.
best regards,
hans
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