From: Andre Fachat (a.fachat_at_gmx.de)
Date: 2002-05-01 20:50:23
Hallo! If you want to be flexible, maybe you want to have a look at my CS/A65 machine. The CPU card has a 74LS610, which maps addresses: The address space is split into 16 blocks with 4k each and the 74LS610 provides 16 registers with 8 bits (actually 9, but the last bit has to be set separately and provides a write-protect bit for the page) that replace the upper 4 address bits: A12-15 --> index in register file --> A12-19 So each of the 16 4k blocks can be mapped from a 1M address space separately. Maybe you also want to include this in your CPU... Andre firstname.lastname@example.org wrote: > > >What about the 6509? That is a 6502 with the difference that it has > >4 more address lines. The output values of the 4 address bits is > >determined by the values of register 0 and 1. register 1 is used for > >the data load and store operations in the lda (),y and sta (),y > >opcodes and reg. 0 otherwise. (r0/r1 maybe vice versa, but in principle > >that is it). > > This chip is indeed and interesting one. The theme could be extended to > include a full 8-bit paging offset, allowing 16MB rather than 1MB access. > For the setting of the register one of the illegal fatal codes could be used > as the operand. > > PLEASE TAKE NOTE: > > The contents of this email (including any attachments) may be > privileged and confidential. Any unauthorised use of the contents > is expressly prohibited. If you have received this email in error, > please advise us immediately (you can contact us by telephone > on +61 8 9441 2311 by reverse charge) and then permanently > delete this email together with any attachments. We appreciate > your co-operation. > > Whilst Orbital endeavours to take reasonable care to ensure > that this email and any attachments are free from viruses or other > defects, Orbital does not represent or warrant that such is explicitly > the case > > (C) 2000: Orbital Engine Company (Australia) PTY LTD and its > affiliates > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing list
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