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Diffstat (limited to 'src/devices/cpu/m37710/m37710.cpp')
-rw-r--r--src/devices/cpu/m37710/m37710.cpp5
1 files changed, 4 insertions, 1 deletions
diff --git a/src/devices/cpu/m37710/m37710.cpp b/src/devices/cpu/m37710/m37710.cpp
index 7aa6b8e2994..15da8e4ae5a 100644
--- a/src/devices/cpu/m37710/m37710.cpp
+++ b/src/devices/cpu/m37710/m37710.cpp
@@ -6,7 +6,7 @@
The 7700 series is based on the WDC 65C816 core, with the following
notable changes:
- - Second accumulator called "B" (on the 65816, "A" and "B" were the
+ - Second 16-bit accumulator called "B" (on the 65816, "A" and "B" were the
two 8-bit halves of the 16-bit "C" accumulator).
- 6502 emulation mode and XCE instruction are not present.
- No NMI line. BRK and the watchdog interrupt are non-maskable, but there
@@ -28,6 +28,9 @@
not the upper 8 bits of X or Y when in 8-bit X. The 7700 preserves
the top bits of all registers in all modes (code in the C74 BIOS
starting at d881 requires this!).
+ - Unlike the 65C816, the program bank register (known here as PG) is
+ incremented when PC overflows from 0xFFFF, and may be incremented or
+ decremented when the address for a relative branch is calculated.
The various 7700 series models differ primarily by their on board
peripherals. The 7750 and later models do include some additional