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Author: sam-falvo

software/src/e2/dxforth/dxforth-boot.asm

@@ -0,0 +1,51 @@
+; DX-Forth Copy Loop
+; Copyright (c) 2017-2019 Samuel A. Falvo II
+; See LICENSE file in this or nearest parent directory.
+;
+; V1.1 : 2018-??-??
+; Initial release for Kestrel-3/E2.
+; BIOS dependency removed; DX-Forth *is* the new BIOS.
+;
+; This code takes control immediately after the CPU boots.
+; Because the Kestrel-3's ROM is so slow (40+ cycles overhead
+; per fetch!), and because the Forth environment was designed
+; to be loaded into RAM for the Kestrel-2DX originally,
+; this loop exists to migrate the contents of DX-Forth in ROM
+; into RAM for final execution.
+
+	include	"regs.i"
+	include "dxforth.regs.i"
+
+
+	; This is the cold-boot entry point of the KCP53K
+	; family of processors.  Our task is to copy the
+	; DX-Forth image to its final resting place in RAM.
+	; Then, jump into RAM to start the DX-Forth image.
+_bios_entry:
+	auipc	gp,0		; GP := 0, basically.
+	lw	a0,_n1-_bios_entry(gp)
+	lw	a1,_n2-_bios_entry(gp)
+	lw	a2,_n3-_bios_entry(gp)
+
+_bios_copy:
+	ld	a3,0(a0)
+	sd	a3,0(a2)
+	addi	a0,a0,8
+	addi	a2,a2,8
+	blt	a0,a1,_bios_copy
+
+_bios_boot:
+	lw	D,_n3-_bios_entry(gp)
+	jalr	x0,0(D)
+
+_n1:	word	_start
+_n2:	word	_end
+_n3:	word	$40000000
+
+	; This is the official starting image of the DX-Forth
+	; program image.  This jump instruction will appear
+	; at $40000000 if all goes according to plan, and this
+	; will then cause DX-Forth to launch.
+_start:
+	incbin	"dxforth-image.bin"
+_end:

software/src/e2/dxforth/dxforth.asm.m4

@@ -12,36 +12,15 @@
 	include	"regs.i"
 	include "dxforth.regs.i"
 
+; Alas, HWORD references within the binary image assume that
+; we load the DX-Forth image on a 64KB boundary.  For this
+; reason, we assemble the DX-Forth body of code as a separate
+; module, with the origin at 0.  We rely on run-time relocation
+; to compute absolute addresses.
+;
+; Just remember to copy this image so that it lies on a 64KB
+; boundary.
 
-	; This is the cold-boot entry point of the KCP53K
-	; family of processors.  Our task is to copy the
-	; DX-Forth image to its final resting place in RAM.
-	; Then, jump into RAM to start the DX-Forth image.
-_bios_entry:
-	auipc	gp,0		; GP := 0, basically.
-	lw	a0,_n1-_bios_entry(gp)
-	lw	a1,_n2-_bios_entry(gp)
-	lw	a2,_n3-_bios_entry(gp)
-
-_bios_copy:
-	ld	a3,0(a0)
-	sd	a3,0(a2)
-	addi	a0,a0,8
-	addi	a2,a2,8
-	blt	a0,a1,_bios_copy
-
-_bios_boot:
-	lw	D,_n3-_bios_entry(gp)
-	jalr	x0,0(D)
-
-_n1:	word	_start
-_n2:	word	_end
-_n3:	word	$40000000
-
-	; This is the official starting image of the DX-Forth
-	; program image.  This jump instruction will appear
-	; at $40000000 if all goes according to plan, and this
-	; will then cause DX-Forth to launch.
 _start:
 	jal	x0,start_dxforth
 
@@ -2214,4 +2193,3 @@ __cm:	jal	W,_docol
 
 	align	8
 _dxforth_end:
-_end:

software/src/e2/dxforth/dxforth.bin.do

@@ -1,3 +1,4 @@
-redo-ifchange ../../../bin/a dxforth.asm
+redo-ifchange ../../../bin/a dxforth.asm dxforth-boot.asm
 exec >&2
-../../../bin/a from dxforth.asm to $3
+../../../bin/a from dxforth.asm to dxforth-image.bin
+../../../bin/a from dxforth-boot.asm to $3