Datasheet

Semihosting

Note

When used with Angel, these SWIs use the serializer and the global register block, and

they can take a significant length of time to process.

5.4.1 SYS_OPEN (0x01)

Open a file on the host system. The file path is specified either as relative to the current

directory of the host process, or absolutely, using the path conventions of the host

operating system.

The ARM targets interpret the special path name

:tt

as meaning the console input

stream (for an open-read) or the console output stream (for an open-write). Opening

these streams is performed as part of the standard startup code for those applications

that reference the C stdio streams.

Entry

On entry, r1 contains a pointer to a three-word argument block:

word 1 This is a pointer to a null-terminated string containing a file or device

name.

word 2 This is an integer that specifies the file opening mode. Table 5-2 gives the

valid values for the integer, and their corresponding ANSI C

fopen()

mode.

word 3 This is an integer that gives the length of the string pointed to by word 1.

The length does not include the terminating null character that must be

present.

SYS_HEAPINFO (0x16) on page 5-25 Get the system heap parameters

SYS_ELAPSED (0x30) on page 5-26 Get the number of target ticks since execution started

SYS_TICKFREQ (0x31) on page 5-26 Determine the tick frequency

Table 5-1 Semihosting SWIs (continued)

SWI Description

Table 5-2 Value of mode

mode 01 2 3 4 5 6 7 89 10 11

ANSI C fopen mode r rb r+ r+b w wb w+ w+b a ab a+ a+b