The stack is mapped to the SAME RAM as the zero page memory.
There are *not* two 128-byte areas of RAM. There is just one.
So, although the stack "lives" at $100 - $1FF, it actually *uses* the RAM
which is also used for your zero-page. That's located from $80 to $FF.
That is, 128 bytes SHARED between the stack and variables. The memory map
below implies differently.
A
----- Original Message -----
From: "Glenn Saunders" <cybpunks@xxxxxxxxxxxxx>
To: <stella@xxxxxxxxxxx>
Sent: Wednesday, June 21, 2000 5:25 PM
Subject: [stella] 2600 Memory Map & Question
> Corrections welcome:
>
>
> <INTERNAL MEMORY>
> <BEGIN PAGE 0>
> Write Address Registers (located inside TIA?)
>
> Addr Assy Name Bits Used Function
>
> 00 Vsync 0000 00x0 Vertical Sync Set-Clear
> 01 Vblank xx00 00x0 Vertical Blank Set-Clear
> 02 Wsync ---- ---- Wait for Horizontal Blank
> 03 Rsync ---- ---- Reset Horizontal Sync Counter
> 04 Nusiz0 00xx 0xxx Number-Size player/missle 0
> 05 Nusiz1 00xx 0xxx Number-Size player/missle 1
> 06 Colup0 xxxx xxx0 Color-Luminance Player 0
> 07 Colup1 xxxx xxx0 Color-Luminance Player 1
> 08 Colupf xxxx xxx0 Color-Luminance Playfield
> 09 Colubk xxxx xxx0 Color-Luminance Background
> 0A Ctrlpf 00xx 0xxx Control Playfield, Ball,
Collisions
> 0B Refp0 0000 x000 Reflection Player 0
> 0C Refp1 0000 x000 Reflection Player 1
> 0D Pf0 xxxx 0000 Playfield Register Byte 0
> 0E Pf1 xxxx xxxx Playfield Register Byte 1
> 0F Pf2 xxxx xxxx Playfield Register Byte 2
> 10 Resp0 ---- ---- Reset Player 0
> 11 Resp1 ---- ---- Reset Player 1
> 12 Resm0 ---- ---- Reset Missle 0
> 13 Resm1 ---- ---- Reset Missle 1
> 14 Resbl ---- ---- Reset Ball
> 15 Audc0 0000 xxxx Audio Control 0
> 16 Audc1 0000 xxxx Audio Control 1
> 17 Audf0 000x xxxx Audio Frequency 0
> 18 Audf1 000x xxxx Audio Frequency 1
> 19 Audv0 0000 xxxx Audio Volume 0
> 1A Audv1 0000 xxxx Audio Volume 1
> 1B Grp0 xxxx xxxx Graphics Register Player 0
> 1C Grp1 xxxx xxxx Graphics Register Player 1
> 1D Enam0 0000 00x0 Graphics Enable Missle 0
> 1E Enam1 0000 00x0 Graphics Enable Missle 1
> 1F Enabl 0000 00x0 Graphics Enable Ball
> 20 Hmp0 xxxx 0000 Horizontal Motion Player 0
> 21 Hmp1 xxxx 0000 Horizontal Motion Player 1
> 22 Hmm0 xxxx 0000 Horizontal Motion Missle 0
> 23 Hmm1 xxxx 0000 Horizontal Motion Missle 1
> 24 Hmbl xxxx 0000 Horizontal Motion Ball
> 25 Vdelp0 0000 000x Vertical Delay Player 0
> 26 Vdelp1 0000 000x Vertical Delay Player 1
> 27 Vdelbl 0000 000x Vertical Delay Ball
> 28 Resmp0 0000 00x0 Reset Missle 0 to Player 0
> 29 Resmp1 0000 00x0 Reset Missle 1 to Player 1
> 2A Hmove ---- ---- Apply Horizontal Motion
> 2B Hmclr ---- ---- Clear Horizontal Move Registers
> 2C Cxclr ---- ---- Clear Collision Latches
>
> Read Address Registers (located inside TIA?)
>
> bit 6 bit 7
> 00 Cxm0p xx00 0000 Read Collision M0-P1 M0-P0
> 01 Cxm1p xx00 0000 M1-P0 M1-P1
> 02 Cxp0fb xx00 0000 P0-PF P0-BL
> 03 Cxp1fb xx00 0000 P1-PF P1-BL
> 04 Cxm0fb xx00 0000 M0-PF M0-BL
> 05 Cxm1fb xx00 0000 M1-PF M1-BL
> 06 Cxblpf x000 0000 BL-PF -----
> 07 Cxppmm xx00 0000 P0-P1 M0-M1
> 08 Inpt0 x000 0000 Read Pot Port 0
> 09 Inpt1 x000 0000 Read Pot Port 1
> 0A Inpt2 x000 0000 Read Pot Port 2
> 0B Inpt3 x000 0000 Read Pot Port 3
> 0C Inpt4 x000 0000 Read Input (Trigger) 0
> 0D Inpt5 x000 0000 Read Input (Trigger) 1
>
> RIOT Memory Map
> 80-FF 128 bytes FREE Ram
>
> </PAGE 0>
>
> <PAGE 1>
> 180-1FF 128 bytes FREE RAM (used primarily as 6507 stack)
> </PAGE 1>
>
> RIOT Hardware registers
> 280 Swcha Port A data register
(joysticks...)
> 281 Swacnt Port A data direction register
(DDR)
> 282 Swchb Port B data (console switches)
> 283 Swbcnt Port B DDR
> 284 Intim Timer output
>
> 294 Tim1t set 1 clock interval
> 295 Tim8t set 8 clock interval
> 296 Tim64t set 64 clock interval
> 297 T1024t set 1024 clock interval
> these are also at 380-397
> </INTERNAL MEMORY>
> --------------------------------------------------------------------------
---------------------
> <EXTERNAL MEMORY>
> Atari 2600 ROM Memory Map
>
> E000-FFFF 8K Rom
> (shouldn't this be EFFF-FFFF? this is an 8K range above)
>
> 1000-1FFF 4K Rom (mirror)
> 3000-3FFF 4K Rom (mirror)
> </EXTERNAL MEMORY>
>
>
> I am curious about something here. The 6507 has a 13-bit address
> bus. This comes out to 8192 bytes linear addressable. Don't these hex
> values jump around too much to fit within that address space?
>
>
> Glenn Saunders - Producer - Cyberpunks Entertainment
> Personal homepage: http://www.geocities.com/Hollywood/1698
> Cyberpunks Entertainment: http://cyberpunks.uni.cc
>
>
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