Vault 7: Projects
This publication series is about specific projects related to the Vault 7 main publication.
Memory Allocation and Access
2012-2013 Microchip Technology Inc. DS50002071C-page 159
10.6.3 Define How to Access Memory Spaces
References to variables placed in external memories are controlled via the use of sev-
eral helper functions. Up to five functions may be defined for reading and five for writ-
ing. One of these functions is a generic routine and will be called if any of the other four
are not defined but are required. If none of the functions are defined, the compiler will
generate an error message. A brief example will be presented in the next subsection.
Generally, defining the individual functions will result in more efficient code generation.
10.6.3.1 FUNCTIONS FOR READING
read_external
void __read_external(unsigned int address,
unsigned int memory_space,
void *buffer,
unsigned int len)
This function is a generic Read function and will be called if one of the next functions
are required but not defined. This function should perform the steps necessary to fill
len bytes of memory in the buffer from the external memory named memory_space
starting at address address.
read_external8
unsigned char __read_external8(unsigned int address,
unsigned int memory_space)
Read 8 bits from external memory space memory_space starting from address
address. The compiler would like to call this function if trying to access an 8-bit sized
object.
read_external16
unsigned int __read_external16(unsigned int address,
unsigned int memory_space)
Read 16 bits from external memory space memory_space starting from address
address. The compiler would like to call this function if trying to access an 16-bit sized
object.
read_external32
unsigned long __read_external32(unsigned int address,
unsigned int memory_space)
Read 32 bits from external memory space memory_space starting from address
address. The compiler would like to call this function if trying to access a 32-bit sized
object, such as a long or float type.
read_external64
unsigned long long __read_external64(unsigned int address,
unsigned int memory_space)
Read 64 bits from external memory space memory_space starting from address
address. The compiler would like to call this function if trying to access a 64-bit sized
object, such as a long long or long double type.
Protego_Release_01_05-Related-OEM-Documentation-MPLAB-XC16-C-Compiler.pdf