Re: use of RBYTE statement to read the keyboard of the HP 9830A


Achim Buerger
 

Rik,

a single option ROM for a 9810/20/30 has 1024 words (2k bytes) size. There are also ROMs for the 9810 which are only 512 words in size (e.g. the Printer Alpha ROM), leaving other half empty. And there are so called combo ROMs for the 9810 which combine two 512 ROMs in one slot, making again 1k words.

The address range depends on the model (in octal numbers)
9810:
slot 1: 02000 - 03777
slot 2: 06000 - 05777
slot 3: 10000 - 11777

9820: total option ROM address space: 10000 - 15777
slot 1: 10000 - 11777
slot 2: 12000 - 13777
slot 3: 14000 - 15777

9830: total option ROM adress space: 17000 - 37777
slot 1: 36000 - 37777
slot 2: 34000 - 35777
slot 3: 20000 - 21777
slot 4: 22000 - 23777
slot 5: 26000 - 27777
slot 6: 17000 - 17777
slot 7: 24000 - 25777
slot 8: 30000 - 31777
slot 9: 32000 - 33777
The slots 6-9 are inside in the housing and slot 6 has only 512 bit adress space.

From this one can see that the address space is machine dependent and in the 9810 also not contigous, which makes adress decoding a bit complicated. Moreover, each ROM slot has its own, fixed adress space.

One could think about incorporating also the system ROMs and replacing the complete system ROM board with a new EPROM board carrying all ROMs and the required decoder and driver logic.

Achim

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