System functions

How to call a system function

By convention (ABI), the function ID must be in the highest a-register (a5). Registers a0 to a4 are for function arguments. Then you can invoke the function either with ecall operation or with the syscall macro (recommended).

The result is returned in a0 registry (sometimes there is an extra information in a1). Error code is returned in a5.

Examples:

.include "consts.s"                # include constants with function names
li a0, '!'                         # load function argument
li a5, SYSFN_PRINT_CHAR            # set function ID
ecall                              # call the function
bnez a5, handle_error              # handle error

.include "consts.s"                # include constants with function names
.include "macros.s"                # include macros
li a0, '!'                         # load function argument
syscall SYSFN_PRINT_CHAR           # call the function with macro
bnez a5, handle_error              # handle error

List of system functions

ID	Name	Const	Description	Status	Ticket
1	sleep	SYSFN_SLEEP	Sleep for n milliseconds	✖
2	idle	SYSFN_IDLE	wait until next event or irq	✅
3	run	SYSFN_RUN	runs program from disc/rom	✅	#53
4	exit	SYSFN_EXIT	exits a program and returns to the system	✅	#53
5	get_cfg	SYSFN_GET_CFG	returns single entry from system config	✅
6	get_drv_cfg	SYSFN_GET_DRV_CFG	returns config of a given driver	✅
10	get_secs_from_epoch	SYSFN_GET_SECS_FROM_EPOCH	Returns number of seconds from 1970/01/01	✅	#8
11	get_date	SYSFN_GET_DATE	Returns current date	✅	#8
12	set_date	SYSFN_SET_DATE	Sets current date	✖
13	get_time	SYSFN_GET_TIME	Returns current time	✅
14	set_time	SYSFN_SET_TIME	Sets current time	✖	#8
20	get_char	SYSFN_GET_CHAR	Get's character from the standard input	✅
21	print_char	SYSFN_PRINT_CHAR	Sends character to a standard output	✅
22	print_str	SYSFN_PRINT_STR	Sends a string to a standard output	✅