First os version with ABI number and working system calls

assembly/applications/README.md

@@ -0,0 +1,12 @@
+# Pat80 Applications
+
+## Intro
+This folder contains some example applications.
+The folder `brief` contains little applications that can be entered directly via keyboard in the memory monitor.
+The folder `big` contains complete applications to be loaded via sdcard or tape.
+
+## How to write an application
+When the Pat80 operating system is built, a `abi-generated.asm` file is built along with the rom binary. This file contains the description of the OS available API.
+An application targeting the last version of the OS should include this file, to make the system calls labels available inside the application code.
+The application can obtain the operating system ABI version (ABI -> https://en.wikipedia.org/wiki/Application_binary_interface) via the Sys_ABI call (it is a 16 bits integer returned in BC).
+The application's first command should be an ABI check: if the OS version is not compatible with the app, the app should exit displaying an error message.

assembly/applications/brief/hello_world.asm

@@ -0,0 +1,7 @@
+org 0xA000
+include '../../bios/abi-generated.asm'
+
+STRING: DB "Hello",0
+ld bc, STRING
+call Sys_Print
+jp 0

assembly/applications/call_printc.asm

@@ -1,3 +0,0 @@
-ld bc, 0xA000
-call 0x0010
-jp 0

assembly/applications/halt_test.asm

@@ -1,9 +0,0 @@
-org 0x00A0
-
-test:
-nop
-nop
-nop
-nop
-nop
-jp test

assembly/applications/hello_world.asm

@@ -1,16 +0,0 @@
-; Prints "Hello world" in terminal
-; Usage: assemble this file with z80asm and insert the resulting bytes
-; via Memory Monitor from address 0xA000 to test SET and RUN commands.
-
-org 0xA000  ; Set starting position to ram
-ld bc, HELLO_WORLD_STR
-Term_print:
-    ld a, (bc)  ; bc is the pointer to string's first char
-    cp 0        ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
-    jp z, term_print_end
-    out (0x00),a    ; output char to IO device 0, addr 0
-    inc bc ; increment bc to move to next char
-    jp Term_print
-	term_print_end:
-	halt
-HELLO_WORLD_STR: DB "Hello world!",0

assembly/bios/Makefile

@@ -2,7 +2,7 @@ bios:
 	@echo "Building PAT80 rom..."
 	@z80asm -i main.asm -o rom.bin || (exit 1)
 	@echo "Generating label lookup table..."
-	@z80asm -i main.asm -o rom.bin -L 2>&1 | grep "Sys_" > rom.label
+	@z80asm -i main.asm -o rom.bin -L 2>&1 | grep "Sys_" > abi-generated.asm
 	@echo "PAT80 Rom size:"
 	@du -h rom.bin
 	@echo "Stretching rom to EEPROM size..."

assembly/bios/README.md

@@ -0,0 +1,15 @@
+# Pat80 Operating System and Memory Monitor
+
+## Intro
+This folder contains the Pat80 Operating System.
+It is a System Monitor that makes available also some system API to access hardware (monitor, sound, keyboard, parallel terminal...).
+
+## Build
+### Requirements
+z80asm, minipro
+### Make
+The os can be build issuing command `make`.
+Two files will be generated:
+- `rom.bin` is the rom file to be flashed on the eeprom
+- `abi-generated.asm` is the file to be included in any Pat80 application to access system APIs (see README.md in ../applications/)
+The build routine will then try to write the rom to a MiniPRO.

assembly/bios/abi-generated.asm

@@ -0,0 +1,6 @@
+Sys_ABI:	equ $0003
+Sys_Beep:	equ $0013
+Sys_Print:	equ $0007
+Sys_Printc:	equ $000a
+Sys_Readc:	equ $000d
+Sys_Readline:	equ $0010

assembly/bios/main.asm

@@ -23,39 +23,37 @@ jp Sysinit     ; Startup vector: DO NOT MOVE! Must be the first instruction
 ; System calls provide access to low level functions (input from keyboard, output to screen etc).
 ; The name starts always with Sys_
 
+; Returns ABI version.
+; (ABI -> https://en.wikipedia.org/wiki/Application_binary_interface)
+; Any Pat80 application should check the ABI version on startup, and refuse to run if not compatible.
+; @return bc the ABI version
+Sys_ABI:
+    ld bc, 0
+    ret
+
 ; Prints string
 ; @param BC Pointer to a null-terminated string first character
-org 0x0010
 Sys_Print:
-    call Term_print
-    ret
+    jp Term_print
 
 ; Writes a single character
 ; @param A Value of character to print
-org 0x0020
 Sys_Printc:
-    call Term_printc
-    ret
+    jp Term_printc
 
 ; Reads a single character
 ; @return A The read character
-org 0x0030
 Sys_Readc:
-    call Term_readc
-    ret
+    jp Term_readc
 
 ; Reads a line
 ; @return BC The pointer to a null-terminated read string
-org 0x0040
 Sys_Readline:
-    call Term_readline
-    ret
+    jp Term_readline
 
 ; Emits system beep
-org 0x0050
 Sys_Beep:
-    call Snd_beep
-    ret
+    jp Snd_beep
 
 
 

assembly/bios/rom.label

@@ -1,5 +0,0 @@
-Sys_Beep:	equ $0050
-Sys_Print:	equ $0010
-Sys_Printc:	equ $0020
-Sys_Readc:	equ $0030
-Sys_Readline:	equ $0040