BBC SHEILA Hardware I/O Addresses
                   =================================

Addr  Write Action                      Read Action
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FE00-FF Electron ULA
====================
FE00  Interupt Control                  Interupt Status
FE01
FE02  (Screen Start)DIV2 Low Byte
FE03  (Screen Start)DIV2 High Byte
FE04  Cassette data shift output        Cassette data shift input
FE05  ROMSEL and interupt clear
FE06  Counter
FE07  Cassette, mode, caps light control
FE08-0F  Palette registers

FE00-07 6845 CTRC Video controller
==================================
FE00  Register Address
FE01  Register Data                     Register Data

FE08-0F 6850 ACIA Serial controller
===================================
FE08  6850 Control                      6850 Status
FE09  6850 Data                         6850 Data

FE10-17 Serial ULA
==================
FE10  Set Baud rate/cassette/motor      -

FE18-1F Station ID/NMI Control (BBC B, B+)
==========================================
FE18  -                                 Station ID, turn off net NMIs

FE18-1F Analogue-to-Digital Convertor (Master)
==============================================
FE18 Start conversion                   Status
FE19                                    Data high byte
FE1A                                    Data low byte
FE1B -                                  -

FE20-2F Video ULA
=================
FE20  Turn network NMIs on (B/B+)      Video Control
FE21                                   Palette Control
FE22                                   Border Colour expansion

FE24-27 Disk control (Master)
=============================
FE24  -                                Drive control register

FE28-2F 1770 Floppy Disk Controller (Master)
============================================
FE28 Status                            Command
FE29 Track                             Track
FE2A Sector                            Sector
FE2B Data                              Data

FE30-3F Memory control
======================
FE30 -                                 ROMSEL

FE34 ACCCON (B+/M)                     ACCON (B+/M)

FE38 Disable network NMIs (Master)     Disable network NMIs (Master)

FE3C Enable network NMIs (Master)      Enable network NMIs (Master)

Solidisk RAM/ROM Expansion
==========================
FE32 RAM Access Register - bank that writes to &8000-BFFF are directed to

FE34 Shadow Register
     b7: 1=VDU and display uses shadow RAM
         0=VDU and display uses main RAM

FE36 Size Register
    00
    10 shadow RAM is 8000-FBFF
    20 shadow RAM is 4000-C000
    40 shadow RAM is 0800-8800
    80 page in upper half of 32K ROM into 16K ROM area

FE40-5F System VIA
==================
FE40 Input register B                  Output register B
FE41 Input register A                  Output register A
FE42 Data direction register B         Data direction register B
FE43 Data direction register A         Data direction register A
FE44 T1 low-order counter              T1 low-order latches
FE45 T1 high-order counter             T1 high-order counter
FE46 T1 low-order latches              T1 low-order latches
FE47 -                                 T1 high-order latches
FE48 T2 low-order counter              T2 low-order latches
FE49 T2 high order counter             T2 high order counter
FE4A Shift register                    Shift register
FE4B Auxilary control register         Auxilary control register
FE4C Peripheral control register       Peripheral control register
FE4D Interupt flag register            Interupt flag register
FE4E Interupt enable register          Interupt enable register
FE4F Input register A, no handshake    Output register A, no handshake

FE60-7F User VIA
================
FE60 Input register B (User port)      Output register B (User port)
FE61 Input register A (Printer port)   Output register A (Printer port)
FE62 Data direction register B         Data direction register B
FE63 Data direction register A         Data direction register A
FE64 T1 low-order counter              T1 low-order latches
FE65 T1 high-order counter             T1 high-order counter
FE66 T1 low-order latches              T1 low-order latches
FE67 -                                 T1 high-order latches
FE68 T2 low-order counter              T2 low-order latches
FE69 T2 high order counter             T2 high order counter
FE6A Shift register                    Shift register
FE6B Auxilary control register         Auxilary control register
FE6C Peripheral control register       Peripheral control register
FE6D Interupt flag register            Interupt flag register
FE6E Interupt enable register          Interupt enable register
FE6F Input register A, no handshake    Output register A, no handshake

FE80-9F 8271 Floppy disk controller
===================================
FE80 Command                            Status
FE81 Parameter                          Result
FE82 Reset                              -
FE83 -                                  -
FE84 Data                               Data

FEA0-BF 6854 ADLC Econet controller
===================================
FEA0 Control register 1                 Status register 1
FEA1 Control register 2,3               Status register 2
FEA2 Transmit data, continue frame      Receive data
FEA3 Transmit data, terminate frame     Receive data

FEC0-DF Analogue-to-digital convertor (B/B+)
============================================
FEC0 Start conversion                   Status
FEC1                                    Data high byte
FEC2                                    Data low byte
FEC3 -                                  -

FEE0-FF Tube control
====================
FEE0 Status Register 1                  Status Register 1
FEE1 Data Register 1                    Data Register 1
FEE2 Status Register 2                  Status Register 2
FEE3 Data Register 2                    Data Register 2
FEE4 Status Register 3                  Status Register 3
FEE5 Data Register 3                    Data Register 3
FEE6 Status Register 4                  Status Register 4
FEE7 Data Register 4                    Data Register 4