bootrom: removed 'ABC' output on UART

[calu.git] / 2_isa / src / bootrom.s

diff --git a/2_isa/src/bootrom.s b/2_isa/src/bootrom.s
index 2a46cfdabb8a38f695b8c955cbfce4607153b502..cb4ac8d8864a1859f82e38ec9ffa61ac1ff94b44 100644 (file)
--- 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
@@ -25,15 +51,11 @@ main:
        ldi r11, PBASE@lo
        ldih r11, PBASE@hi
 poll:
-       ldw r3, UART_STATUS(r10)
-       andx r3, UART_RECV_NEW
-       brzs+ poll; branch if zero
-
        call recv_byte
        ; we received the enter bootrom sign
        xor r1, r1, r1
        cmpi r0, 0x48 ; 'H'
-       breq- bt_H
+       breq+ bt_H
        br poll ; else
 
 ;-----
@@ -41,7 +63,7 @@ send_byte:
        ldw r3, UART_STATUS(r10)
        andx r3, UART_TRANS_EMPTY
        brnz+ send_byte ; branch if not zero
-       stb r1, UART_TRANS(r10)
+       stw r1, UART_TRANS(r10)
        ret
 
 ;-----
@@ -62,7 +84,7 @@ recv_byte:
        andx r3, UART_RECV_NEW
        brzs+ recv_byte; branch if zero
        xor r0, r0, r0
-       ldb r0, UART_RECV(r10)
+       ldw r0, UART_RECV(r10)
        ret
 
 ;-----
@@ -81,22 +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
-       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
@@ -114,10 +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
@@ -126,18 +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'
@@ -154,7 +178,4 @@ bt_T:
        br bootrom
 
 bt_J:
-       call recv_word
-       brr r0
-
-tehend:
+       ; 'overflow' ROM