diff options
Diffstat (limited to 'src/devices/cpu/m37710/m37710.cpp')
-rw-r--r-- | src/devices/cpu/m37710/m37710.cpp | 5 |
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 |