PART : CHIP SELECTION 
Project Helios  Specification  Memory Controller / DMA CHIP  CHIP SELECTION

This part give you many information about the chip selection and the hard compatibility with ORIC ATMOS

CARTOGRAPHY OF THE MEMORY


Table I : Mapping of Helios memory
NORMAL MODE
0x000000 - 0x00FFFFSTACK POINTER (64 KBytes)
0x010000 - 0x01FFFFORIC EMULATION(64 KBytes)
0x020000 - 0x02FFFFI/O SPACE (64 KBytes)
0x030000 - 0xAFFFFFUSER RAM (10,81 MBytes)
0xB00000 - 0xBFFFFFDSP (1 MBytes)
0xC00000 - 0xDFFFFFRAM VIDEO + RAM SOUND (2 MBytes)
0xE00000 - 0xFFFFFFROM (2 MBytes)


Table II : Mapping of ORIC ATMOS
ORIC ATMOS
0x0000 - 0x00FFpage 0
0x0100 - 0x01FFpage 1 (stack)
0x0200 - 0x02FFpage 2 (variables)
0x0300 - 0x03FFpage 3 I/O space
0x0400 - 0x97FFUSER RAM
0x9800 - 0xBFDFVIDEO RAM
Text & Graphic
0xBFE0 - 0xBFFFnot used
0xC000 - 0xFFFFROM


Table III : Remapping of memory when Helios emulates ORIC ATMOS
EMULATION MODE
0x000000 - 0x0000FFremapped in 0x010000 - 0x010000
0x000100 - 0x0001FFremapped in 0x010100 - 0x0101FF
0x000200 - 0x0002FFremapped in 0x010200 - 0x0102FF
0x000300 - 0x0003FFremapped in 0x020300 - 0x0203FF
0x000400 - 0x0097FFremapped in 0x010400 - 0x0197FF
0x009800 - 0x00BFDFremapped in 0xC00000 - 0xC027DF
0x00BFE0 - 0x00BFFFremapped in 0x01BFE0 - 0x01BFFF
0x00C000 - 0x00FFFFremapped in 0x01C000 - 0x01CFFF & RD only authorized


EXPLANATION
The µprocessor 65816 has an output pin named E. It indicates if the µprocessor is in emulation mode or normal mode.

MODE NORMAL, pin E = 0
 In this mode, the µcomputer run not to compatible mode but in normal mode.

EMULATION MODE, pin E = 1
 When the pin E is equal at 1, the µprocessor is in emulation mode. In this mode, the hardware translate the adress memory following the table III. During this phase, a register from memory controller has set at a bank number from 0x02 TO 0xAF.
 In fact, Helios runs in emulation mode but it can switchs to the normal mode ! This is a pseudo-multitasking in my mind.
CHIP SELECTION

This part of the project generates all need signals to select :

The boolean equation of the part depend from the state of the pin E ( from 65C816).

Hypothese 1 : PIN E = 0 : Normal Mode.
  1. ROM FLASH = |A23 & |A22 & |A21 & |A20
  2. RAM DSP = |A23 & |A22 & A21 & A20
  3. CHIP I/O = ROM FLASH & (A19 & A18 & A17 & |A16)
  4. RAM VIDEO = |A23 & |A22 & A21 & |A20 & |RAM DSP & |ROM FLASH
  5. RAM DYNAMIC = (A23 & A22 & A21 & A20 & A19 & A18 & A17 & A16) & |CHIP I/O & |RAM DSP & |RAM VIDEO & |RAM DSP

Hypothese 2 : PIN E = 1 :  Emulation Mode.

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