Decouple shell from acia

parts/README.md

@@ -35,4 +35,18 @@ Thus, code that glue parts together coould look like:
     MOD2_RAMSTART .equ MOD1_RAMEND
     #include "mod2.asm"
 
+## Code style
+
+The asm code used in these parts is heavily dependent on what scas offers. I
+try to be as "low-tech" as possible because the implementation of the assembler
+to be implemented for the z80 will likely be more limited. For example, I try
+to avoid macros.
+
+One exception, however, is for the routine hooks (`SHELL_GETC` for example). At
+first, I wanted to assign a label to a const (`SHELL_GETC .equ aciaGetC` for
+example), but it turns out that scas doesn't support this (but it could: label
+addresses are known at compile time and thus can be consts (maybe at the cost
+of an extra pass though)). I went for macros instead, but that doesn't mean
+that the z80 assembler will need to support macros. It just need to support
+labels-as-consts.
 [scas]: https://github.com/KnightOS/scas

parts/acia.asm

@@ -115,7 +115,7 @@ aciaGetC:
 	call	aciaIncIndex
 	ld	(ACIA_BUFRDIDX), a
 
-	; And finially, fetch the value.
+	; And finally, fetch the value.
 	ld	a, (de)
 
 	pop	de

parts/shell.asm

@@ -1,20 +1,23 @@
 ; shell
 ;
-; Runs a shell over an asynchronous communication interface adapter (ACIA).
-; for now, this unit is tightly coupled to acia.asm, but it will eventually be
-; more general than that.
+; Runs a shell over an block device interface.
 
 ; Status: incomplete. As it is now, it spits a welcome prompt, wait for input
 ; and compare the first 4 chars of the input with a command table and call the
 ; appropriate routine if it's found, an error if it's not.
 ;
-; Commands, for now, are dummy.
+; Commands, for now, are partially implemented.
 ;
 ; See constants below for error codes.
 ;
 ; All numerical values in the Collapse OS shell are represented and parsed in
 ; hexadecimal form, without prefix or suffix.
 
+; *** DEFINES ***
+; SHELL_GETC: Macro that calls a GetC routine
+; SHELL_PUTC: Macro that calls a PutC routine
+; SHELL_RAMSTART
+
 ; *** CONSTS ***
 
 ; number of entries in shellCmdTbl
@@ -61,7 +64,7 @@ shellInit:
 
 shellLoop:
 	; First, let's wait until something is typed.
-	call	aciaGetC
+	SHELL_GETC
 	; got it. Now, is it a CR or LF?
 	cp	ASCII_CR
 	jr	z, .do		; char is CR? do!
@@ -100,9 +103,9 @@ shellLoop:
 
 printcrlf:
 	ld	a, ASCII_CR
-	call	aciaPutC
+	SHELL_PUTC
 	ld	a, ASCII_LF
-	call	aciaPutC
+	SHELL_PUTC
 	ret
 
 ; Parse command (null terminated) at HL and calls it

recipes/rc2014.md

@@ -67,6 +67,8 @@ init:
 ACIA_RAMSTART	.equ	RAMSTART
 #include "acia.asm"
 SHELL_RAMSTART	.equ	ACIA_RAMEND
+.define SHELL_GETC	call aciaGetC
+.define SHELL_PUTC	call aciaPutC
 #include "shell.asm"
 ```
 
@@ -89,6 +91,10 @@ What comes below is actual code include from parts we want to include in our
 OS. As you can see, we need to tell each module where to put their variables.
 See `parts/README.md` for details.
 
+You can also see from the `SHELL_GETC` and `SHELL_PUTC` macros that the shell
+is decoupled from the ACIA and can get its IO from anything. See
+`parts/README.md` for details.
+
 ### Build the image
 
 We only have the shell to build, so it's rather straightforward: