Much more information will be available in the near future! Until then, enjoy this 
summary of the Turbo/PCE memory mapping. 

Memory Mapping 




The HuC6280 has a 64KB logical address space and a 2MB physical address space. 
To access this entire memory space, the processor depends on 8 memory mapping registers, 
known as MPR0 - MPR7. These registers map each 8KB segment of the logical address space 
to an 8KB segment in the physical address space. 



Thus, the first block of memory, $0000 - $1FFF, is mapped using MPR0. 
The next segment, $2000 - $3FFF, is mapped using MPR1, and so on. 
These registers are set using the special TAM and TMA opcodes, described in the opcode section. 



Memory Segment          MPR #          TAM / TMA argument 
$E000 - $FFFF             7              10000000 
$C000 - $DFFF             6              01000000 
$A000 - $BFFF             5              00100000 
$8000 - $9FFF             4              00010000  
$6000 - $7FFF             3              00001000 
$4000 - $5FFF             2              00000100 
$2000 - $3FFF             1              00000010 
$0000 - $1FFF             0              00000001 







To form the physical address, the three high order bits from the logical address are 
used to select an MPR. The 8 bits in the MPR then become the high order bits of the 
address, thus forming a 21-bit physical address from a 16-bit logical address. 



Here's an example, showing how the address $3F13 is mapped 
to physical address $1F1F13 using MPR1: 



See memmap1.jpg<Image>



The 2MB physical address space available to the HuC6280 contains all of the 
memory-mapped I/O necessary to interface with the other chips, the CD subsystem, 
and the user (through the HuCard and joystick ports). Below is the full memory map 
for the TurboGrafx / PC Engine family. Each segment is labeled with its corresponding 
MPR register value ($00 - $FF), a description of the segment's use, 
its physical address location, and a "chip enable signal" or other descriptive text. 
The Develo Book describes the chip enable signal as an external signal that becomes 
true when that area of memory is accessed. Currently, it is not known if these signals 
correspond with any pins or traces available on the system motherboard. Signals 
in parentheses, such as (/CEP), represent chip enable signals that are internal to 
the HuC6280. The notation /SIGNAME is equivalent to a negative logic signal; that is, 
the signal is active when it is low instead of high. 







Physical Addresses          Segment #          Description          Chip Enable Signal 
1FFC00 - 1FFFFF            FF           Reserved for Expansion 
1FF800 - 1FFBFF            "             Reserved for Expansion 
1FF400 - 1FF7FF            "         Interrupt Req./Disable Registers      (/CECG) 
1FF000 - 1FF3FF            "                    I/O Ports                  (/CEIO) 
1FEC00 - 1FEFFF            "                   TIMER Ports                 (/CET) 
1FE800 - 1FEBFF            "                     PSG Ports                 (/CEP) 
1FE400 - 1FE7FF            "                  HuC6260 Ports                 /CEK 
1FE000 - 1FE3FF            "                  HuC6270 Ports                 /CE7  
1FC000 - 1FDFFF            FE 
1FA000 - 1FBFFF            FD 
1F8000 - 1F9FFF            FC 
1F2000 - 1F7FFF          F9 - FB                                            /CER 
1F0200 - 1F1FFF            F8              Base "scratchpad" RAM              " 
1F0100 - 1F01FF             "                  Stack Page                     " 
1F0000 - 1F00FF             "                  Zero Page                      "
1EE000 - 1EFFFF            F7           Last page of HuCard memory 
004000 - 1EDFFF         02 - F6             HuCard storage 
002000 - 003FFF            01 
001FFE - 001FFF            00                Reset Vector 
001FFC - 001FFD             "                 NMI Vector 
001FFA - 001FFB             "                 TIMER Vector 
001FF8 - 001FF9             "                 IRQ1 Vector 
001FF6 - 001FF7             "                 IRQ2 Vector (for BRK) 
000000 - 001FF5             "           First page of HuCard memory