Service manual

Chapter 4 E01 Circuit description
FileStore Service Manual 21
4.13.3 Address decoding
The main decoding component are IC11, IC14, IC18 and IC1. These supply the decoding to
support the software activity as follows.
The layout of the file server memory map is as follows:
From To Function
0 &FF Zero page, see suballocation below
&100 &1FF Hardware stack
&200 &3FF MOS workspace
&400 &7BFF file server and print server code if loaded
&7C00 &E7FF file and print server workspace
&E800 &FBFF MOS code
&FC00 &FCFF Memory mapped I/O, see suballocation below
&FD00 &FFE2 MOS code
&FFE3 OSASCI entry
&FFE7 OSNEWL entry
&FFEE OSWRCH entry
&FFF1 OSWORD entry
&FFF4 OSBYTE entry
&FFFA NMI vector
&FFFC RST vector
&FFFE IRQ vector
Page zero is suballocated as follows:
From To Function
&00 &1F spare (some locations used if debug options enabled in MOS)
&20 &8F file server/ print server workspace
&90 &9F spare at present, but may be allocated to file server
&A0 &AF Econet driver workspace
&B0 &BF file server workspace
&C0 &DF Econet driver workspace
&E0 &FF Disc handler workspace
Page &FC (the memory mapped I/O page) is suballocated as follows:
&FC00[-&FC03] 146818 RTC address register
&FC04[-&FC07] 146818 RTC data register
&FC08[-&FC0B] (read) ROM/RAM memory access latch (currently will always will
select RAM, but moving a jumper makes it toggle).
&FC08[-&FC0B] (write) miscellaneous function latch
&FC0C-&FC0F 2793 floppy Disc Controller
&FC10-&FC1F 6522 Versatile Interface Adaptor
&FC20-&FC23 6854 Econet interface disabled
&FC24[-&FC27] Econet interrupt disable
&FC28[-&FC2B] Econet interrupt enable
&FC2C[-&FC2F) floppy drive door switch state
&FC30-&FC33 FileStore expansion bus interface. Strapped to emulate bus address
&40. The bottom two bits of the &FC3x address indicate bus &4x.