cs176sbd@sdcc3.ucsd.EDU (I-Teh Hsieh) (06/05/88)
Is there a scheme which would allow the HP-85 and the HP-9816 operate on the same bus (IEEE 488, HP1B) exchanging the role of controlling the bus and the instruments or peripherals on the bus? Would one computer be allowed to control the bus while setting the other idle and vice versa? Thanks. I-Teh
rer@hpfcdc.HP.COM (Rob Robason) (06/10/88)
> Is there a scheme which would allow the HP-85 and the HP-9816 operate > on the same bus (IEEE 488, HP1B) exchanging the role of controlling > the bus and the instruments or peripherals on the bus? Would one > computer be allowed to control the bus while setting the other idle > and vice versa? Thanks. Yes. Both the 9816 and 85 can be configured as non-system controllers. A typical technique is to use the 9816 as shipped, with the HP-IB on select code 7 and the interface set to address 21. Open the 85 HP-IB card and, using to owners manual for the card as a reference, configure it as a NON-system controller, and set the address to something other than the default 21, like 20 (so it doesn't conflict with the 9816 address). Now hook the two HP-IB interfaces together and to your instruments. At the beginning, the 9816 will have control of the bus, being both system and active controller. The 85 should do an "ON INTERRUPT 7..." with appropriate configuration to respond to receiving control of the bus with an interrupt. (I've forgotten the details, but they're in the manual.) When the 9816 wants to relenquish the bus it does a PASS CONTROL to 720, the 85 is now active controller. Now the 9816 needs to respond to receiving control as the 85 did, so that it interrupts when the 85 passes control. The reset of the interface or system on the 9816 will return active control to the system controller (9816). Hope this helps. Rob Robason Former 85/9816 hacker