Talk:RAMBO-1: Difference between revisions
From NESdev Wiki
Jump to navigationJump to search
(→replica watches: new section) |
(→Alternate Method for RAMBO-1 IRQ: new section) |
||
| (18 intermediate revisions by 4 users not shown) | |||
| Line 1: | Line 1: | ||
As for the 2mb PRG, I'm not sure if the cart actually supports that much ROM, but the PRG registers apparently are 8 bits, and 8kb * $100 = 2048kb = 2mb. --[[User:Drag|Drag]] 03:05, 9 November 2011 (UTC) | As for the 2mb PRG, I'm not sure if the cart actually supports that much ROM, but the PRG registers apparently are 8 bits, and 8kb * $100 = 2048kb = 2mb. --[[User:Drag|Drag]] 03:05, 9 November 2011 (UTC) | ||
== | == Alternate IRQ timing == | ||
This is how to get 4 games working: Klax, Skull&Crossbones, Rolling Thunder and Hard Drivin'. | |||
*Address mask: $E001. | |||
writes to $C000: irq_latch=data; | |||
writes to $C001: irq_reload=true; irq_mode=data&1; | |||
writes to $E000: irq_enable=false; IRQ acknowledge by CPU. | |||
writes to $E001: irq_enable=true; IRQ acknowledge by CPU. | |||
* When the IRQ is clocked by CPU or scanline modes: | |||
If irq_reload == true: | |||
irq_counter = irq_latch; | |||
if irq_latch != 0 | |||
irq_counter |= 1; | |||
irq_reload=false; | |||
Else if irq_counter == 0: | |||
irq_counter = irq_latch; | |||
Else | |||
irq_counter--; | |||
If irq_counter == 0 and irq_enable == true | |||
irq_delay=4 (IRQ will be fired 4 CPU cycles later) | |||
== Alternate Method for RAMBO-1 IRQ == | |||
Nintendulator-NRS's source file /mappers/src/iNES/mapper064.cpp has an alternative implementation of the IRQ which allows it to work properly with all known games to use it: Klax, Skull & Crossbones and Hard Drivin'. | |||
Latest revision as of 14:43, 9 July 2019
As for the 2mb PRG, I'm not sure if the cart actually supports that much ROM, but the PRG registers apparently are 8 bits, and 8kb * $100 = 2048kb = 2mb. --Drag 03:05, 9 November 2011 (UTC)
Alternate IRQ timing
This is how to get 4 games working: Klax, Skull&Crossbones, Rolling Thunder and Hard Drivin'.
- Address mask: $E001.
writes to $C000: irq_latch=data; writes to $C001: irq_reload=true; irq_mode=data&1; writes to $E000: irq_enable=false; IRQ acknowledge by CPU. writes to $E001: irq_enable=true; IRQ acknowledge by CPU.
- When the IRQ is clocked by CPU or scanline modes:
If irq_reload == true:
irq_counter = irq_latch;
if irq_latch != 0
irq_counter |= 1;
irq_reload=false;
Else if irq_counter == 0:
irq_counter = irq_latch;
Else
irq_counter--;
If irq_counter == 0 and irq_enable == true
irq_delay=4 (IRQ will be fired 4 CPU cycles later)
Alternate Method for RAMBO-1 IRQ
Nintendulator-NRS's source file /mappers/src/iNES/mapper064.cpp has an alternative implementation of the IRQ which allows it to work properly with all known games to use it: Klax, Skull & Crossbones and Hard Drivin'.
