X-Git-Url: http://wien.tomnetworks.com/gitweb/?a=blobdiff_plain;f=2_isa%2Fsrc%2Fbootrom.s;h=cb4ac8d8864a1859f82e38ec9ffa61ac1ff94b44;hb=9e0cdea8077967ceb02ec9ffa04c31eb46e82c88;hp=d38e1854527f517791893b82811e21e057a93780;hpb=e342529c0374b6173bd50f346c088fc7e5eccfdc;p=calu.git

diff --git a/2_isa/src/bootrom.s b/2_isa/src/bootrom.s
index d38e185..cb4ac8d 100644
--- a/2_isa/src/bootrom.s
+++ b/2_isa/src/bootrom.s
@@ -1,3 +1,29 @@
+;* bootROM, a very small bootloader for $NAME
+;*
+;* protocol details:
+;* abbrv: H = Host, CPU = C
+;*
+;* value/cmd              | direction | comment
+;* ------------------------------------------------------------
+;* 'H'                    | H -> C    | enter bootROM ("HI")
+;* 'O'                    | C -> H    | ack bootROM entry ("OH HAI")
+;*
+;* 'W'0xZZZZZZZZ0xYYYYYYYY| H -> C    | write instr (0xYY...Y) to
+;*                                    | address (0xZZ...Z)
+;* 'D'                    | C -> H    | instr write done
+;*
+;* 'R'0xZZZZZZZZ          | H -> C    | read instr from address (0xZZ..Z)
+;* 'F'0xYYYYYYYY          | C -> H    | instr read done and return instr
+;*
+;* 'Q'0xZZZZZZZZ0xYYYYYYYY| H -> C    | write data (0xYY...Y) to
+;*                                    | address (0xZZ...Z)
+;* 'A'                    | C -> H    | data write done
+;*
+;* 'T'0xZZZZZZZZ          | H -> C    | read data from address (0xZZ..Z)
+;* 'G'0xYYYYYYYY          | C -> H    | read done and return data
+;*
+;* 'J'0xZZZZZZZZ          | H -> C    | jump to address (0xZZ...Z)
+;*/
 	.data
 
 	.text
@@ -77,24 +103,21 @@ recv_word:
 
 	call recv_byte
 	lls r1, r1, 8
-	or r1, r0, r1
+	or r0, r0, r1
+	xor r1, r1, r1
 
-	addi r0, r1, 0
 	ret
 
 ;-----
 bootrom:
 	call recv_byte
-	ldi r1, 0x50 ; 'P'
-	call send_byte
-	br tehend
-
 	xor r1, r1, r1
+
 	cmpi r0, 0x57 ; 'W'
 	breq- bt_W
 
-	cmpi r0, 0x52 ; 'R'
-	breq- bt_R
+	;cmpi r0, 0x52 ; 'R'
+	;breq- bt_R
 
 	cmpi r0, 0x51 ; 'Q'
 	breq- bt_Q
@@ -112,10 +135,11 @@ bootrom:
 bt_H:
 	ldi r1, 0x4f ; 'O'
 	call send_byte
-	call send_byte
 	br bootrom
 
 bt_W:
+	ldi r1, 0x57 ; 'W'
+	call send_byte
 	call recv_word ; receive addr
 	stw r0, PADDR(r11)
 	call recv_word ; receive instr
@@ -124,18 +148,20 @@ bt_W:
 	call send_byte
 	br bootrom
 
-bt_R:
-	call recv_word ; receive addr
-	mov r2, r0
-	ldi r1, 0x46 ; 'F'
-	call send_byte
-	ldx r1, 0(r2)
-	call send_word
-	br bootrom
+;bt_R: ;lesen von IRAM wird nicht unterstuetzt
+	;call recv_word ; receive addr
+	;mov r2, r0
+	;ldi r1, 0x46 ; 'F'
+	;call send_byte
+	;ldx r1, 0(r2)
+	;call send_word
+	;br bootrom
 
 bt_Q:
+	ldi r1, 0x51 ; 'Q'
+	call send_byte
 	call recv_word ; receive addr
-	mov r6, r0
+	addi r6, r0, 0
 	call recv_word ; receive data
 	stw r0, 0(r6)
 	ldi r1, 0x41 ; 'A'
@@ -152,7 +178,4 @@ bt_T:
 	br bootrom
 
 bt_J:
-	call recv_word
-	brr r0
-
-tehend:
+	; 'overflow' ROM