From: ian <ian>
Date: Sun, 20 Nov 2005 00:04:21 +0000 (+0000)
Subject: fixes and changes from code review
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ijackson/git?a=commitdiff_plain;h=1c858ec502540aef1a83f0ae49153d43503be6de;p=trains.git

fixes and changes from code review
---

diff --git a/detpic/panic.asm b/detpic/panic.asm
index 9f30685..29bf2c9 100644
--- a/detpic/panic.asm
+++ b/detpic/panic.asm
@@ -12,15 +12,16 @@
 
 	udata_acs
 
+; used in panic routine for temporary storage:
+
 flash_pattern		res	1
 morse_counter		res	1
 register_counter	res	1
 bit_counter		res	1
 
-; used in panic macro for temporary storage
-panic_address	res	1	; stores condensed form of message start addr.
-panic_morse	res	1	; stores # bytes of morse msg in panic readout
-panic_regs	res	1	; stores # registers in panic readout
+panic_address	res	1	; condensed form of message start addr.
+panic_morse	res	1	; # bytes of morse msg in panic readout
+panic_regs	res	1	; # registers in panic readout
 
 
 ;****************************************************************************
@@ -29,10 +30,6 @@ panic_regs	res	1	; stores # registers in panic readout
 
 ;****************************************************************************
 
-; first, copy the panic message address out of WREG  
-
-        mov_wf   panic_address
-
 panic_routine
 ; switch off interrupts and power
 ; reconfigure timer0 for writing diagnostic msg to the LED
@@ -40,6 +37,12 @@ panic_routine
         clr_f    INTCON        ; disable all interrupts EVER
         bc_f     PORTC,1       ; switch off booster
 
+; now we have time to copy the panic message address out of WREG
+; (turning off interrupts is urgent (we might get interrupted while
+;  panicing which would be bad because we might forget to panic).
+
+        mov_wf   panic_address
+
 
 ; re-initialise timer0 config
         bc_f     T0CON,6       ; p107 Timer0 -> 16bit mode
@@ -53,7 +56,7 @@ panic_routine
 ; back from condensed message start addr. stored in panic_address
 
 panic_loop
-	mov_lw	4
+	mov_lw	4 ; size of each message's details
 	mul_wf	panic_address
 	mov_ff	PRODL,TBLPTRL		
 	mov_ff	PRODH,WREG
@@ -78,7 +81,7 @@ panic_loop
 	call	waiting
 	call	waiting
 	call	waiting
-	call	morsemsg	; transmit SOS in red
+	call	morsemsg	; transmit morse in red
 	call	led_black
 	call	waiting
 	call	waiting
@@ -92,8 +95,7 @@ panic_loop
 ; PANIC SUBROUTINES
 
 morsemsg
-; wrapper round readout to flash the per-pic led red for a
-; (currently 4-byte) morse msg
+; wrapper round morse_readout to flash the per-pic led red for a morse msg
 
 morse_msg_start
 	clr_f		morse_counter		; clear loop counter
@@ -113,7 +115,7 @@ morse_loop
 ;--------------------------
 morse_readout
 
-; Flashes the per-pic led red(0) in a specified pattern.
+; Flashes the per-pic led and black in a specified pattern.
 ;
 ; The pattern is specified as the state for 8 identically-long time
 ; periods each as long as a morse `dot', encoded into a byte with
@@ -123,13 +125,14 @@ morse_readout
 ; flash_pattern		flash pattern		preserved
 ; bit_counter		any			undefined
 
-	clr_f		bit_counter		; clear loop counter
+	mov_lw		8
+	mov_wf		bit_counter
 	rr_f		flash_pattern
 
 morse_readout_loop
-	mov_fw		panic_regs
-	cmp_fw_ifge	bit_counter		; if loop counter >=panic_regs, return
+	dec_f_ifz	bit_counter		; done all the bits yet ?
 	return
+	; No:
 
 	rl_f		flash_pattern		; top bit goes into N, 
 						;ie Negative if 1
@@ -143,8 +146,6 @@ morse_readout_if_led_1
 	call		led_red
 
 morse_readout_endif_led
-	inc_f		bit_counter		; increment loop counter
-	call		waiting
 	bra		morse_readout_loop
 
 ;--------------------------
@@ -201,21 +202,21 @@ register_readout
 
 
 register_readout_loop
-        movlw   	8
+        mov_lw   	8
         cmp_fw_ifge 	bit_counter         	; if loop counter >=8 (register 
 						; length), return
         return
 
-        movlw   	4
+        mov_lw   	4
         cmp_fw_ifne	bit_counter	; if loop counter !=4 (nybble length), 
 					; skip insertion of extra black space
 	goto		not_nybble_boundary
 	call		waiting
 
 not_nybble_boundary
-        rlncf   	flash_pattern,1         ; top bit goes into N flag, 
+        rl_f	   	flash_pattern           ; top bit goes into N flag, 
 						; ie Negative if 1
-        bn      	register_readout_if_led_1
+        bra_n      	register_readout_if_led_1
 
 register_readout_if_led_0
         call    	led_red
@@ -243,9 +244,9 @@ waiting
         clr_f  	TMR0H         	; p107 set high byte of timer0 to 0 (buffered,
                                 ; only actually set when write to tmr0l occurs)
         clr_f  	TMR0L         	; set timer0 low byte - timer now set to 0000h
-loop
+waiting_loop
         bt_f_if0 INTCON,TMR0IF    	
-        bra     loop		; wait for timer0 interrupt
+        bra     waiting_loop	; wait for timer0 interrupt
         return