From: ian <ian>
Date: Wed, 21 Dec 2005 13:18:46 +0000 (+0000)
Subject: check for receiving too much nmra data
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ijackson/git?a=commitdiff_plain;h=b11ea0f4e84ebec8b3a380ed2ce1a8964f2919ca;p=trains.git

check for receiving too much nmra data
---

diff --git a/detpic/morse.messages b/detpic/morse.messages
index 8ce7148..234af1d 100644
--- a/detpic/morse.messages
+++ b/detpic/morse.messages
@@ -20,10 +20,13 @@
 
 # Miscellaneous
 E				; `expected'; we were told to panic
+
+# Regarding communications from the host
 HX	::t			; host sent unknown command
 HW	::t			; host sent message which was too long
 HO				; host RS232 read overrun
 HF				; host RS232 framing error
+HN				; host sent too much NMRA - buffers full
 
 # Problematic interrupts
 IH	INTCON,INTCON3,PIR1,PIR2,PIR3 ; Interrupt source not found (high pri.)
diff --git a/detpic/nmra-stream.asm b/detpic/nmra-stream.asm
index f88fbf4..dedc299 100644
--- a/detpic/nmra-stream.asm
+++ b/detpic/nmra-stream.asm
@@ -221,9 +221,8 @@ fixme need to check both interrupt handlers here and look for refies too
 serial_receive_done
 	intrl_handled_nostack
 
-receive_message_too_long
-	panic	morse_HW
- fixme reviewed up to here for inclusion in bigger program
+receive_too_much_nmra		panic	morse_HW
+receive_message_too_long	panic	morse_HW
 
 ; *** I *think* the interrupt bit is cleared by reading out of RCREG
 ; but this may be something to try in debugging if stuff doesn't work
@@ -244,10 +243,24 @@ advance_write_buffer
 	debug 	'5'
 	mov_fw	fromserial		; W =		00BB0000
 	add_lw	0x10			; W =		0?CC0000
-	bc_w	6			; W =		00CC0000
-	mov_wf	fromserial		;  where BB is this buffer
+	mov_wf	t			; t =		0?CC0000
+					;  where BB is this buffer
 					;   and CC is next buffer
- fixme check for overruns ie if we caught up with totrack
+
+	; we have to check our proposed new value for fromserial
+	; against totrack before we store it in fromserial;
+	; otherwise there's the possibility that we will store
+	; the new value, and then the high-priority ISR will
+	; interrupt us and advance totrack onto the buffer we've
+	; just filled, fooling us into thinking we've overrun.
+	xor_wfw	totrack			; W =		0?DD????
+	and_lw	0x30			;		..DD....
+	bra_z	receive_too_much_nmra	; where DD is (fromserial buffer)
+					;  xor (totrack buffer)
+
+	mov_wf	t			; W =		0?CC0000
+	bc_w	6			; W =		00CC0000
+	mov_fw	fromserial
 
 	bra	serial_receive_done
 
@@ -258,6 +271,7 @@ not_nmra_message
 	bra	serial_receive_done
 
 ;****************************************************************************
+ fixme reviewed up to here for inclusion in bigger program
 
 nmra_interrupt_timer
 	bt_f_if0 INTCON,2,0	; check whether timer0 interrupt set