avr: added some comments.

avr/modules/flash/flash1p.asm

@@ -97,10 +97,14 @@ Flash_WriteData_done:
 ; @clobbers R16, R18, R24, R25, X (R0, R1, R19, R20)
 
 flashWriteData:
+  rcall flashCheckCurrentValid         ; (r18, r19)
+  brcc flashWriteData_beginPage
+
   rcall flashWriteCheckPage            ; (r18, r19)
-  brcs flashWriteData_calcPosAndLength
+  brcs flashWriteData_calcPosAndLength ; still inside current page, jump
   rcall flash1pEndPage                 ; (R0, R1, R16, R18, R19, R20, R24, R25, X)
-  rcall flash1pBeginPage               ; (r16, r24, r25, X, Z)
+flashWriteData_beginPage:
+  rcall flash1pBeginPage               ; (r16, r24, r25, X)
 flashWriteData_calcPosAndLength:
   rcall flashCalcPosAndLength          ; (r24, r25)
   ; X=abs pos in buffer, r18=bytes to read, r17=bytes initially requested
@@ -135,11 +139,11 @@ flashCalcPosAndLength:
   ldi r25, FLASH_PAGESIZE
   sub r25, r24                   ; r25=bytes left inside page
   mov r18, r17
-  cp r25, r17
-  brcc flashCalcPosAndLength_l1
-  mov r18, r25
+  cp r25, r17                    ; bytes to read > bytes left in page?
+  brcc flashCalcPosAndLength_l1  ; no: jump
+  mov r18, r25                   ; yes: cut r18 to number of bytes left in page
 flashCalcPosAndLength_l1:
-  ldi xl, LOW(flashPageBuffer)
+  ldi xl, LOW(flashPageBuffer)   ; set X to pos within page buffer
   ldi xh, HIGH(flashPageBuffer)
   add xl, r24
   adc xh, r24
@@ -155,6 +159,7 @@ flashCalcPosAndLength_l1:
 ; check whether the given address is inside the current page in buffer
 ;
 ; @return CFLAG set if same page, cleared otherwise
+; @param Z address to write to
 ; @clobbers r18, r19
 
 flashWriteCheckPage: