Talk:RAMBO-1: Difference between revisions
From NESdev Wiki
Jump to navigationJump to search
m (Deleted obsoleted IRQ speculation.) |
(→Alternate Method for RAMBO-1 IRQ: new section) |
||
| (4 intermediate revisions by 2 users not shown) | |||
| Line 15: | Line 15: | ||
If irq_reload == true: | If irq_reload == true: | ||
irq_counter = irq_latch; | irq_counter = irq_latch; | ||
if | if irq_latch != 0 | ||
irq_counter |= 1; | |||
irq_reload=false; | irq_reload=false; | ||
Else if irq_counter == 0: | Else if irq_counter == 0: | ||
| Line 24: | Line 25: | ||
irq_delay=4 (IRQ will be fired 4 CPU cycles later) | 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'.
