VRAM access interface

Read / Write VRAM. More...

Collaboration diagram for VRAM access interface:

Typedefs
typedef uint32_t	vmemptr_t
	Type for VRAM address.

Functions
void	vmem_set_read_address (vmemptr_t loc)
	MSX Set VRAM address for sequential reading of VRAM.
void	vmem_set_write_address (vmemptr_t loc)
	MSX Set VRAM address for sequential writing of VRAM.
uint8_t	vmem_get (void)
	MSX Read 1 byte from VRAM.
void	vmem_set (uint8_t val)
	MSX Write 1 byte to VRAM.
void	vmem_read (vmemptr_t src, void *dst, uint16_t len)
	MSX Read a series of bytes from VRAM.
void	vmem_write (vmemptr_t dst, void *src, uint16_t len)
	MSX Write a series of bytes to VRAM.
void	vmem_memset (vmemptr_t dst, uint8_t val, uint16_t len)
	MSX Fill a series of bytes in VRAM with the specified value.

Detailed Description

Read / Write VRAM.

Typedef Documentation

vmemptr_t

typedef uint32_t vmemptr_t

Type for VRAM address.

Definition at line 42 of file vmem.h.

Function Documentation

vmem_set_read_address()

void vmem_set_read_address

(

vmemptr_t

loc

)

MSX Set VRAM address for sequential reading of VRAM.

This function sets the VRAM access base address register (R#14) and/or the VRAM address counter to a value based on loc for sequential reading of VRAM in subsequent calls to vmem_get().

Parameters

loc	VRAM address.

See also

vmem_get()

vmem_set_write_address()

void vmem_set_write_address

(

vmemptr_t

loc

)

MSX Set VRAM address for sequential writing of VRAM.

This function sets the VRAM access base address register (R#14) and/or the VRAM address counter to a value based on loc for sequential writing of VRAM in subsequent calls to vmem_set().

Parameters

loc	VRAM address.

See also

vmem_set()

vmem_get()

uint8_t vmem_get ( void  )

inline

MSX Read 1 byte from VRAM.

Returns

a value read from VRAM.

Note

vmem_set_read_address() must be called at least once, before calling vmem_get(). Also, after the last call to vmem_set_read_address() and before calling vmem_get(), vmem_set_write_address() must not be called.

See also

vmem_set_read_address()

vmem_read()

Definition at line 83 of file vmem.h.

vmem_set()

void vmem_set ( uint8_t  val )

inline

MSX Write 1 byte to VRAM.

Parameters

val	a value to be written to VRAM.

Note

vmem_set_write_address() must be called at least once, before calling vmem_set(). Also, after the last call to vmem_set_write_address() and before calling vmem_set(), vmem_set_read_address() must not be called.

See also

vmem_set_write_address()

vmem_write()

Definition at line 100 of file vmem.h.

vmem_read()

void vmem_read	(	vmemptr_t	src,
		void *	dst,
		uint16_t	len
	)

MSX Read a series of bytes from VRAM.

This function copies len bytes from VRAM to RAM.

That is almost same as the below code:

vmem_set_read_address(src);
for (uint8_t *p = dst; len--; ) {
  *p++ = vmem_get();
}

Parameters

src	source base address of VRAM.
dst	destination base address of RAM.
len	number of bytes to be read.

vmem_write()

void vmem_write	(	vmemptr_t	dst,
		void *	src,
		uint16_t	len
	)

MSX Write a series of bytes to VRAM.

This function copies len bytes from ROM/RAM to VRAM.

That is almost same as the below code:

vmem_set_write_address(dst);
for (uint8_t *p = src; len--; ) {
  vmem_set(*p++);
}

Parameters

dst	destination base address of VRAM.
src	source base address of ROM/RAM.
len	number of bytes to be written.

vmem_memset()

void vmem_memset	(	vmemptr_t	dst,
		uint8_t	val,
		uint16_t	len
	)

MSX Fill a series of bytes in VRAM with the specified value.

That is almost same as the below code:

vmem_set_write_address(dst);
for (; len--; ) {
  vmem_set(val);
}

Parameters

dst	destination base address of VRAM.
val	a byte value to be written.
len	number of bytes to be written.