Notes On Computech Integra-B
----------------------------

In order to use the additional RTC, Shadow, Private & Sideways RAM which the
Integra-B offers, the IBOS ROM must first be loaded. The ROM should be
placed in the beebfile\bbcint dirctory and will be loaded as the highest
priority ROM, bank 15. ROM bank 14 will be loaded with BASIC, and all other
ROMS will be loaded into ROM banks 13 downwards.  BeebEm comes
pre-configured with this ROM setup.

Integra-B comes configured with 4 16K Shadow RAM banks as standard (banks
4,5,6 & 7), although this can be changed if required. If any ROMS are loaded
into these banks and the ROM write protect is removed, then the contents of
these ROMS can be overwritten.

The emulators RTC will read the correct time from the PCs internal clock,
but the emulator has not been configured to alter the PCs internal clock
when attempting to write the time to the RTC.

When the IntegraB mode is selected following will be seen:

Computech INTEGRA-B 128K
Watford DFS (If loaded)
BASIC
>

BeebEm will default the IntegraB to select language 14 and OSMODE 4.  Typing
'*HELP' will give a list of commands which are available under IBOS.

There are a total of 6 OSMODEs available:

	0	standard BBC model B without Shadow Ram
	1	standard BBC model B with Shadow Ram
	2	BBC models B+ and B+ 128 (Rom ids W..Z are 12..15)
	3	BBC Master 128
	4	BBC models B+ and B+ 128
	5	BBC Master Compact

There are two registers to support memory allocations under INTEGRA OS
control. These are duplicated to facilitate bit changing and return to a
prior state following an interrupt service routine. The registers and their
locations are as follows:

	ROMSEL	at $FE30	ROM select latch
	ROMID	at $00F4	Ram copy of ROMSEL
	RAMSEL	at $FE34	RAM select latch
	RAMID	at $037F	Ram copy of RAMSEL

Internal organisation of there registers is:

ROMSEL & ROMID
	Bits 0,1,2,3	ROMNUM	Sideways ROM/RAM select bits
	Bits 4,5		Not used
	Bit 6		PRVEN	Private RAM enable
	Bit 7		MEMSEL	Shadow/Main RAM toggle

RAMSEL & RAMID
	Bits 0,1	AUX0,1	Not used but must be preserved
	Bits 2,3		Not used
	Bit 4		PRVS1	Private RAM 8K area select
				(&9000-&AFFF)
	Bit 5		PRVS4	Private RAM 4K area select
				(&8000-&8FFF)
	Bit 6		PRVS8	Private RAM 1K area select
				(&8000-&83FF)
	Bit 7		SHEN	Shadow Ram enable bit

PRVEN and PRVS1,4 & 8 are used together to overlay sections sections of the
currently selected Sideways ROM or RAM with private RAM. This means that
Software in Sideways ROM or RAM can have direct access to the private RAM.

SHEN and MEMSEL are used together to determine whether Main/Video memory or
the Shadow Ram is paged into the area &3000 to &7FFF:

	Control Bits		Memory area selected
       SHEN    MEMSEL		 &3000-&7FFF

	0	 X		 Main/Video Memory
	1	 0		 Shadow Memory
	1	 1		 Main/Video Memory
