ZXSTGS

Contains the Z80 registers and other internal state information for the General Sound Interface.

Memory state is stored separately in ZXSTGSRAMPAGE blocks which will follow this block.

// General Sound

// Flags
#define ZXSTZF_EILAST         1
#define ZXSTZF_HALTED         2
#define ZXSTGSF_CUSTOMROM     64
#define ZXSTGSF_COMPRESSED    128

// GS model
#define ZXSTGSM_128   0
#define ZXSTGSM_512   1

typedef struct _tagZXSTGS
{
  ZXSTBLOCK blk;
  BYTE chModel;
  BYTE chUpperPage;
  BYTE chGsChanVol[4];
  BYTE chGsChanOut[4];
  BYTE chFlags;
  WORD AF, BC, DE, HL;
  WORD AF1, BC1, DE1, HL1;
  WORD IX, IY, SP, PC;
  BYTE I;
  BYTE R;
  BYTE IFF1, IFF2;
  BYTE IM;
  DWORD dwCyclesStart;
  BYTE chHoldIntReqCycles;
  BYTE chBitReg;
  BYTE chRomData[1];
} ZXSTGS, *LPZXSTGS;

Members

blk

The block header. The block id is ZXSTBID_GS ('G', 'S', 0, 0 ).

chModel

The GS model being emulated. This can be one of:

Value	Meaning
ZXSTGSM_128	General Sound with 128KB of RAM.
ZXSTGSM_512	General Sound with 512KB of RAM.

chUpperPage

The current 32KB RAM (or ROM if 0) page at $8000 - $ffff.

chGsChanVol[4]

The 6-bit volume level of each of the four sound channels. Bits 6 and 7 should be set to zero.

chGsChanOut[4]

The output level to each of the four sound channels.

chFlags

Various flags indicating the internal state of the interface. This can be a combination of:

Flag	Meaning
ZXSTZF_EILAST	The last instruction executed was an EI instruction.
ZXSTZF_HALTED	The last instruction executed was a HALT instruction. The CPU is currently executing NOPs and will continue to do so until the next interrupt occurs. This flag is mutually exclusive with ZXSTZF_EILAST.
ZXSTGSF_CUSTOMROM	A custom GS ROM is installed. The ROM image begins at chRomData. The default ROM is version 1.04.
ZXSTGSF_COMPRESSED	If a custom GS ROM is embedded in this block, it has been compressed with the Zlib compression library.

AF

The contents of the AF register pair

BC

The contents of the BC register pair

DE

The contents of the DE register pair

HL

The contents of the HL register pair

AF1

The contents of the AF' register pair

BC1

The contents of the BC' register pair

DE1

The contents of the DE' register pair

HL1

The contents of the HL' register pair

IX

The contents of the IX register pair

IY

The contents of the IY register pair

SP

The contents of the stack pointer, SP

PC

The current value of the program counter, PC

I

The contents of the R register

R

The contents of the R register

IFF1

The value of Interrupt Flip Flop 1 (IFF1). This is guaranteed to be either 0 or 1.

IFF2

The value of Interrupt Flip Flop 2 (IFF2). This is guaranteed to be either 0 or 1.

IM

The current Z80 interrupt mode. This can be 0, 1 or 2.

dwCyclesStart

The t-states value at the time the snapshot was made. This counts up from zero to the maximum number of t-states per 50Hz frame.

chHoldIntReqCycles

The number of t-states left on restart when an interrupt can occur. This is used to support interrupt re-triggering properly.

chBitReg

Internal Z80 register used to generate bits 5 and 3 of the F register after executing a BIT x,(HL) instruction.

chRomData

A Zlib compressed or uncompressed custom GS ROM (if one was installed). The uncompressed ROM size is always 32,768 bytes. When loading Zlib compressed ROMs, the compressed size can be obtained by:

compressedSize = blk.dwSize - ( sizeof( ZXSTGS ) - 1 - sizeof( ZXSTBLOCK ));

Remarks

Memory state is stored separately in ZXSTGSRAMPAGE blocks which will follow this block.

Revision history

Available since version 1.2.