Extend possible range of OS_Call[After|Every]

OS_CallAfter and OS_CallEvery were treating the delay in R0 as a signed number, limiting its possible range. The PRM didn't require this (a -ve delay doesn't make sense, so implicitly times are unsigned), reworked to allow times up to 0xFFFFFBFF.
Aside:
  OSLib exports these functions as 'int', but it doesn't seem to make a distinction for unsigned versus signed anyway (other unsigned arguments are plain int too)
  The 'callx' library was already prototyped with unsigned times back in 1997

Added comment to hdr/Options about FirstUnpluggableModule - since the keyboard and mouse drivers got moved out of the kernel in 3.50, the original intent (to not allow you to unplug vital modules) has long since been lost, and really the only use of this value is to save 8 bits of CMOS frugal bits.

Version 5.35, 4.79.2.181. Tagged as 'Kernel-5_35-4_79_2_181'

VersionASM

@@ -13,11 +13,11 @@
                         GBLS    Module_ComponentPath
 Module_MajorVersion     SETS    "5.35"
 Module_Version          SETA    535
-Module_MinorVersion     SETS    "4.79.2.180"
-Module_Date             SETS    "10 Jan 2013"
-Module_ApplicationDate  SETS    "10-Jan-13"
+Module_MinorVersion     SETS    "4.79.2.181"
+Module_Date             SETS    "17 Jan 2013"
+Module_ApplicationDate  SETS    "17-Jan-13"
 Module_ComponentName    SETS    "Kernel"
 Module_ComponentPath    SETS    "castle/RiscOS/Sources/Kernel"
-Module_FullVersion      SETS    "5.35 (4.79.2.180)"
-Module_HelpVersion      SETS    "5.35 (10 Jan 2013) 4.79.2.180"
+Module_FullVersion      SETS    "5.35 (4.79.2.181)"
+Module_HelpVersion      SETS    "5.35 (17 Jan 2013) 4.79.2.181"
                         END

VersionNum

@@ -5,19 +5,19 @@
  *
  */
 #define Module_MajorVersion_CMHG        5.35
-#define Module_MinorVersion_CMHG        4.79.2.180
-#define Module_Date_CMHG                10 Jan 2013
+#define Module_MinorVersion_CMHG        4.79.2.181
+#define Module_Date_CMHG                17 Jan 2013
 
 #define Module_MajorVersion             "5.35"
 #define Module_Version                  535
-#define Module_MinorVersion             "4.79.2.180"
-#define Module_Date                     "10 Jan 2013"
+#define Module_MinorVersion             "4.79.2.181"
+#define Module_Date                     "17 Jan 2013"
 
-#define Module_ApplicationDate          "10-Jan-13"
+#define Module_ApplicationDate          "17-Jan-13"
 
 #define Module_ComponentName            "Kernel"
 #define Module_ComponentPath            "castle/RiscOS/Sources/Kernel"
 
-#define Module_FullVersion              "5.35 (4.79.2.180)"
-#define Module_HelpVersion              "5.35 (10 Jan 2013) 4.79.2.180"
+#define Module_FullVersion              "5.35 (4.79.2.181)"
+#define Module_HelpVersion              "5.35 (17 Jan 2013) 4.79.2.181"
 #define Module_LibraryVersionInfo       "5:35"

hdr/Options

@@ -329,8 +329,8 @@ ConfiguredLang  SETA    10
 
                 GBLA    FirstUnpluggableModule
 FirstUnpluggableModule  SETA 8                  ; Podule, FileSwitch, ResourceFS, Messages, MessageTrans,
-                                                ; TerritoryManager, UKTerritory
-
+                                                ; TerritoryManager, UK. Moot now the keyboard and mouse aren't
+                                                ; in the kernel - unplug those and you're stuffed.
  [ DebugForcedReset
 Reset_CannotResetFlag           * 1
 Reset_SysHeapCorrupt            * 2

s/TickEvents

@@ -17,23 +17,27 @@
 ; This file revised by TMD 28-Jan-94 to
 ; a) Correct internals to time n ticks not n+1
 ; b) Change externals to add 1 to compensate for user subtracting 1
-; c) Fix RemoveTickerEvent to add this nodes time onto the next one
+; c) Fix RemoveTickerEvent to add this node's time onto the next one
 ; These fix bug MED-02498.
 
 ; There are two (centisecond) ticker SWIs :
 ; SWI CallAfter calls the given address once, after the given number of ticks
 ; SWI CallEvery  "     "    "    "      every N centiseconds
 
-; In :  R0 is (signed) number of centiseconds
+; In :  R0 is unsigned number of centiseconds
 ;       R1 is address to call
 ;       R2 is value of R12 to pass to code
 
+CallEvery_Code
+        ADD     r10, r0, #1             ; compensate for n+1 bug
+        B       TickTockCommon
 CallAfter_Code   ROUT
         MOV     r10, #0
 TickTockCommon
         Push    "r0-r3, lr"
-        CMP     r0, #0
-        BLE     %FT99
+        ADD     r14, r0, #1024
+        CMP     r14, #1024
+        BLS     %FT99                   ; reject 0 and >= &FFFFFC00
 
   [ ChocolateSysHeap
         ASSERT  ChocolateTKBlocks = ChocolateBlockArrays + 8
@@ -72,9 +76,6 @@ TickTockCommon
 
         MakeErrorBlock BadTime
 
-CallEvery_Code
-        ADD     r10, r0, #1             ; compensate for n+1 bug
-        B       TickTockCommon
 
 ; Data structure :
 ; chain of nodes
@@ -111,8 +112,8 @@ InsertTickerEvent   ROUT
 ; R1 is node pointer, R0 ticks to wait
 ; R10-R12 corrupted
 
-        Push    "r0,r2"
-        PHPSEI  r2
+        Push    "r0,lr"
+        PHPSEI  r14
         LDR     r10, =ZeroPage+TickNodeChain
 01
         MOV     r11, r10
@@ -120,9 +121,9 @@ InsertTickerEvent   ROUT
         CMP     r10, #0
         BEQ     %FT02                           ; end of chain
         LDR     r12,  [r10, #TickNodeLeft]
-        SUBS    r0, r0, r12
-        BGE     %BT01
-        ADD     r0, r0, r12
+        CMP     r12, r0
+        SUBLS   r0, r0, r12
+        BLS     %BT01                           ; node R10 is earlier (or equal) to node R1
         SUB     r12, r12, r0
         STR     r12, [r10, #TickNodeLeft]
 02
@@ -130,9 +131,8 @@ InsertTickerEvent   ROUT
         STR     r0, [r1, #TickNodeLeft]
         STR     r10, [r1, #TickNodeLink]
 
-        PLP     r2
-        Pull    "r0,r2"
-        MOV     pc, lr
+        PLP     r14
+        Pull    "r0,pc"
 
 ProcessTickEventChain  ROUT
 ; R0-R3, R10-R12 corruptible
@@ -145,7 +145,7 @@ ProcessTickEventChain  ROUT
         LDR     r2, [r1, #TickNodeLeft]
         SUBS    r2, r2, #1
         STR     r2, [r1, #TickNodeLeft]
-        MOVGT   pc, lr                          ; nothing to call yet (was MOVPL)
+        MOVNE   pc, lr                          ; nothing to call yet (was MOVPL)
 
         Push    "lr"                            ; save IRQ_lr
  [ TickIrqReenter
@@ -166,7 +166,7 @@ ProcessTickEventChain  ROUT
 
         LDR     r0, [r1, #TickNodeRedo]
         CMP     r0, #0                          ; CallEvery?
-        BLE     %FT05
+        BEQ     %FT05
 
         BL      InsertTickerEvent               ; yes, then re-insert timer
         B       %FT10
@@ -191,15 +191,15 @@ ProcessTickEventChain  ROUT
   ]
         WritePSRc SVC_mode+I_bit, r1            ; IRQ's off again
 
-; Check for more events down the list
+; Check for more events at the same level in the list
 10
         LDR     r1, [r3, #TickNodeLink]         ; get top of list
         CMP     r1, #0                          ; list empty?
         BEQ     %FT02                           ; yes then exit
 
         LDR     r0, [r1, #TickNodeLeft]
-        CMP     r0, #0                          ; timed out?
-        BLE     %BT01                           ; yes then jump
+        CMP     r0, #0                          ; zero time delta?
+        BEQ     %BT01                           ; yes then jump
 02
         Pull    "lr"                            ; restore SVC_lr
         WritePSRc IRQ_mode+I_bit, r10           ; back to IRQ mode