228 lines
5.3 KiB
Markdown
228 lines
5.3 KiB
Markdown
# System Calls
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The system API is exposed to user code using the COP interrupt.
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The B accumulator is loaded with a function number;
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the other registers are loaded with call-specific data (or nothing),
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and any return values are placed in the same registers.
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What follows is a list of the system calls, their numbers, and
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register arguments they take, and what if any values they return.
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The system API is based loosely on, but not compatible with, that of
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CP/M-3 and MSX-DOS 2.
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## 0x00: Terminate with Error Code
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Arguments:
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C: 0x00
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X: Error code
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Return Values:
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This call does not return.
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This call exits the calling program, setting the exit status code
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for the system on its way out. Program control will be returned to
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the command shell.
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## 0x01: Console Input
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Arguments:
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C: 0x01
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Return Values:
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C: Character read from stdin
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This call reads one character from standard input. If there is no character
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ready, this call waits until there is one. The read character will also be
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echoed to the screen, just as if it had been passed to the Console Output
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call.
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This call traps certain sequences of characters for "terminal control"
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purposes. When this call traps such a character, it outputs nothing an
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continues waiting for another character to be ready.
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## 0x02: Console Output
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Arguments:
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C: 0x02
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X: Character to output
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Return Values:
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None
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This call sends a single chracter to the standard output, which is usually
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the terminal emulator. The character will be parsed by the terminal emulator
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to handle control characters and escape sequences.
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## 0x03: Direct Console Input
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Arguments:
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C: 0x03
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Return Values:
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C: Character value
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This call does direct (raw) console input; if there is a character ready, it
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will be read, and if not, NULL will be returned.
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## 0x04: Direct Console Output
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Arguments:
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C: 0x04
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X: Character value
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Return Values:
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C: Character value
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This call does direct (raw) console output; the value supplied will be treated
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as the value to write to screen memory, and will not be interpreted for terminal
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control.
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## 0x05: String Output
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Arguments:
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C: 0x05
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X: Address of string (15:0)
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Y: Address of string (23:16)
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Return Values:
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None
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This call uses the 0x02 call "Console Output" above to send a NULL-terminated
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string to stdout.
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## 0x06: Buffered Line Input
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Arguments:
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C: 0x06
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X: Address of buffer (15:0)
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Y: Address of buffer (23:16)
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Return values:
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C: Error code
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This call will read up to 255 characters from stdin, or up to the first newline,
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whichever comes first. While taking input, a simple line editor is presented to
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the user. When the 255th character has been entered into the buffer, any further
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input will be ignored until a newline is entered.
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The newline in the resulting buffer will be replaced with a NULL to terminate the
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string.
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## 0x07: Console Status
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Arguments:
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C: 0x07
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Return Values:
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C: Status Code
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This call checks stdin for a character to read. If there is none, this call will return
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zero in A; if there is a character ready, it will return nonzero in A.
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## 0x08: Return Version Number
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Arguments:
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C: 0x08
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Return Values:
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C: Major version
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X: Minor version
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Y: Micro version
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This call returns the version number of the kernel.
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## 0x09: Get Date
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Arguments:
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C: 0x09
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X: Bank of buffer
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Y: Address of buffer
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Return Values:
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None
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This call fills in the specified buffer with the current date,
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in the following format:
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struct {
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uint16_t year // Current year
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uint8_t month; // 1 = January..12 = December
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uint8_t day; // 1..31
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uint8_t weekday; // 0 = Sunday..6=Saturday
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}
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## 0x0A: Set Date
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Arguments:
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C: 0x0A
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X: Bank of buffer
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Y: Address of buffer
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Return Values:
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None
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This call sets the system date from the data in the specified buffer,
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which must be in the following format:
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struct {
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uint16_t year // Current year
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uint8_t month; // 1 = January..12 = December
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uint8_t day; // 1..31
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uint8_t weekday; // 0 = Sunday..6=Saturday
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};
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## 0x0B: Get Time
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Arguments:
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C: 0x0B
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X: Bank of buffer
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Y: Address of buffer
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Return Values:
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None
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This call fills in the specified buffer with the current time,
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in the following format:
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struct {
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uint8_t hour; // 0..23
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uint8_t minute; // 0..59
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uint8_t second; // 0..59
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};
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## 0x0C: Set Time
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Arguments:
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C: 0x0C
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X: Bank of buffer
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Y: Address of buffer
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Return Values:
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None
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This call sets the current time from the provided buffer, which must
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be in the following format:
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struct {
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uint8_t hour; // 0..23
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uint8_t minute; // 0..59
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uint8_t second; // 0..59
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};
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## 0x0D: Open File
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Arguments:
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C: 0x0D
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X: Bank of pathname string
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Y: Address of pathname string
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Return Values:
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C: File handle or error code
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This call attempts to open the file referred to by the provided NULL-terminated
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string, which must contain a fully-qualified pathname -- something of the form
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`[drive]:/[dir]/[dir2]/filename.ext`, such as `sd0:/games/kaboom/readme.ansi`.
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If the file is successfully opened, the carry flag will be cleared and the C
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accumulator will contain the file handle. On error, the carry flag will be |