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Further improve exposition.

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This commit is contained in:
Thomas Harte 2022-09-09 15:48:25 -04:00
parent 2edbbfbe37
commit 45dc99fb9d
1 changed files with 30 additions and 7 deletions
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37
Processors/65816/Implementation/65816Storage.hpp
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@ -281,13 +281,36 @@ struct ProcessorStorage {
// Flags aplenty.
MOS6502Esque::LazyFlags flags;
uint8_t mx_flags[2] = {1, 1}; // [0] = m; [1] = x. In both cases either `0` or `1`; `1` => 8-bit.
uint16_t m_masks[2] = {0xff00, 0x00ff}; // [0] = src mask (i.e. that which is unaffected by an operation); [1] = dst mask (i.e. 0xffff ^ src mask).
uint16_t x_mask = 0x00ff; // A mask representing the current size of the index registers. Equivalent to m_masks[1].
uint16_t e_masks[2] = {0xff00, 0x00ff}; // Akin to m_masks, but set as per emulation mode.
int m_shift = 0; // How far to shift memory/A to align its sign bit with that of the flags register. i.e. 8 for 16-bit mode, 0 for 8-bit mode.
int x_shift = 0; // m_shift equivalent for X and Y.
bool emulation_flag = true; // The emulation flag; true = in emulation mode.
// [0] = m; [1] = x. In both cases either `0` or `1`; `1` => 8-bit.
uint8_t mx_flags[2] = {1, 1};
// Used to determine which parts of a register are currently in use, as a function
// of the M flag.
//
// [0] = src mask (i.e. that which is unaffected by an operation);
// [1] = dst mask (i.e. 0xffff ^ src mask).
//
// e.g. a LDA from the value Q would prima facie leave A as equal to:
// (A & m_masks[0]) | (Q & m_masks[1]);
uint16_t m_masks[2] = {0xff00, 0x00ff};
// A mask representing the current size of the index registers.
// Equivalent in meaning to m_masks[1] but representative of the X flag.
uint16_t x_mask = 0x00ff;
// Akin to m_masks, but a function of emulation mode; used primarily for address calculation.
uint16_t e_masks[2] = {0xff00, 0x00ff};
// How far to shift memory/A to align its sign bit with that of the flags register.
// i.e. 8 for 16-bit mode, 0 for 8-bit mode.
int m_shift = 0;
// m_shift equivalent for X and Y.
int x_shift = 0;
// The emulation flag; true = in emulation mode.
bool emulation_flag = true;
// The offset for direct addressing (i.e. outside of emulation mode).
uint16_t direct = 0;