Memory

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Detailed Description

The MCU ATmega128 has three different types of memory:

1. PROGMEM - program memory, flash technology, size 128KB
2. RAM - 4KB
3. EEPROM - 4KB

TODO external 256KB SRAM

Some of the functions can access any of the memories.

Memory model

For developer following functions simplify the memory access:

• u8 rb(const void *addr) - read one byte from address addr.
• u16 rw(const void *addr) - read one word from address addr.
• void wb(void *addr, u8 val) - write one byte (=val) to address addr.
• void ww(void *addr, u16 val) - write one word (=val) to address addr.

For wb() and ww() only the RAM or EEPROM makes sence.

Memory allocation

For RAM allocation you can use the standard malloc(), free() calls and

 #include <stdlib.h> 

To access EEPROM you must use emalloc(), efree() calls.

On PROGMEM

To insert some data into PROGMEM in compilation time you can use the attribute PROGMEM. Example:

u8 PROGMEM data[]={0,1,2,3};

includes {0,1,2,3} into PROGMEM.

To access such data you must use rb() or rw() calls.

u8 PROGMEM data[]={0,1,2,3};
u8 x;
u8 i;

for(i=0;i<sizeof(data);i++) x=rb(data+i);

Attention:

Because or very little RAM we suggest to put everything possible into PROGMEM, esp. strings.

There is a very little stack so use malloc()/free() rather than local arrays.

For details on PROGMEM please refer to AVR LIBC documentation.

Typedefs

• typedef unsigned char u8
• typedef unsigned short u16
• typedef unsigned long u32
• typedef char b8
• typedef short b16
• typedef long b32

Functions

• void * emalloc (u16 size)
• void efree (void *ptr)
• u8 rb (const void *addr)
• void wb (void *addr, u8 val)
• u16 rw (const void *addr)
• void ww (void *addr, u16 val)
• void reg_app_data (void *data)
• void * app_data (void)
• u8 ext_sram_rb (u32 addr)
• void ext_sram_wb (u32 addr, u8 value)
• u8 * buf_A (void)
• u8 * buf_B (void)

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Typedef Documentation

typedef short b16

signed 2bytes=16bits

typedef long b32

signed 4bytes=32bits

typedef char b8

signed 1byte=8bits

typedef unsigned short u16

unsigned 2bytes=16bits

typedef unsigned long u32

unsigned 4bytes=32bits

typedef unsigned char u8

unsigned 1byte=8bits Examples: sim/utils-src/sim_dump.c.

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Function Documentation

void* app_data (  void   )

Return pointer on application persistent data.

u8* buf_A (  void   )

Pointer on buffer 1072 bytes long. Can be used only during one action. Content can be rewritten between actions. Examples: avrprog/module-src/avrprog.c, df/module-src/df.c, sim/module-src/sim.c, and turboadapter/module-src/turboadapter.c.

u8* buf_B (  void   )

Pointer on buffer 1072 bytes long. Can be used only during one action. Content can be rewritten between actions.

void efree (  void *  ptr  )

Free emalloc'ed chunk. Parameters: ptr

void* emalloc (  u16  size  )

Same as malloc but in EEPROM. Parameters: size

u8 ext_sram_rb (  u32  addr  )

Read byte from extern 256KB SRAM. Parameters: addr

void ext_sram_wb (  u32  addr, u8  value )

Write byte to extern 256KB SRAM. Parameters: addr  value

u8 rb (  const void *  addr  )

Read byte from memory. Parameters: addr  EEPROM, PROGMEM, RAM memory address.

void reg_app_data (  void *  data  )

Store (in EEPROM) pointer on application persistent data. Parameters: data

u16 rw (  const void *  addr  )

Read word from memory. Parameters: addr  EEPROM, PROGMEM, RAM memory address.

void wb (  void *  addr, u8  val )

Write byte to memory. Parameters: addr  EEPROM, RAM memory address. val  value.

void ww (  void *  addr, u16  val )

Write word to memory. Parameters: addr  EEPROM, RAM memory address. val  value.