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author Robbbert <Robbbert@users.noreply.github.com>2020-08-12 23:29:04 +1000
committer Robbbert <Robbbert@users.noreply.github.com>2020-08-12 23:29:04 +1000
commit30d0813c4603da03c3e702da9ba4cf85291a825d (patch)
tree58264ae734a4ddca55f90670ffd3324747deadc1
parentc4a184e2c6716ff05f474733544586eb501285f9 (diff)
parentf36df9216a3b1ce9b154c45c1404e9c419c69438 (diff)
Merge branch 'master' of https://github.com/mamedev/mame into master
-rw-r--r--src/mame/drivers/unk6502_st2xxx.cpp6
1 files changed, 5 insertions, 1 deletions
diff --git a/src/mame/drivers/unk6502_st2xxx.cpp b/src/mame/drivers/unk6502_st2xxx.cpp
index e64a255872f..14362245560 100644
--- a/src/mame/drivers/unk6502_st2xxx.cpp
+++ b/src/mame/drivers/unk6502_st2xxx.cpp
@@ -9,10 +9,14 @@
// these games were ported to unSP hardware at some point, see generaplus_gpl_unknown.cpp
// BIOS calls are made very frequently to the undumped firmware.
-// The most common call ($6058 in bbl380, $6062 in ragc153 & dphh8630) seems to involve downloading a snippet of code from Flash and executing it from RAM.
+// The most common call ($6058 in bbl380, $6062 in ragc153 & dphh8630) seems to involve downloading a snippet of code from Flash and executing it from RAM at $0300.
// A variant of this call ($60d2 in bbl380, $60e3 in ragc153 & dphh8630) is invoked with jsr.
// For these calls, a 24-bit starting address is specified in $82:$81:$80, and the length in bytes is twice the number specified in $84:$83.
// ST2205U cannot execute code directly from Flash, but has a built-in DMA-compatible NAND interface on Port F ($05).
+// The XOR used on ragc153 & dphh8630 is likely performed by the DMA controller.
+// $6003 performs a table lookup, depositing a sequence of data at $008e.
+// $6000 generates some duration of delay based on the X register.
+// One other BIOS call ($6975 in bbl380, $69d2 in ragc153) has an unknown purpose.
#include "emu.h"