chekmate@athena.mit.edu (Adam Kao) (12/07/89)
Hello,
Dave Kaffine sent me this to post for him. As noted, please reply to
him, not me.
Adam
================================
NOTE: I don't have access to the news, so I'm having a friend post this for
me. Please send any responses or questions to the address below, not
to any address you may find in the header.
Here is a partial memory map for the HP-28S. It starts at the bottom of
RAM, and continues to the beginning of user variables at the top of RAM,
filling in details for everything I've figured out so far. In the
map, lower addresses are toward the right and toward the top (because
that's the way things look when I use my routines to display a screenful
of data). Any specific ROM addresses shown are for version 2BB.
I hope my format is comprehensible. If anyone can fill in any of the gaps,
or point out corrections, please post!
Dave Kaffine davek01%cs@ncr-fc.ftcollins.ncr.com
or kaffine_d%cubldr@vaxf.colorado.edu
Fixed location system storage:
F E D C B A 9 8 7 6 5 4 3 2 1 0
-----------------------------------------------------------------
| 48-bit timer value (updated each minute) | KEYMASK | C0000
-----------------------------------------------------------------
register by interrupt service routine | ? | CALIB. FACTOR C0010
-----------------------------------------------------------------
register by interrupt service routine | Storage for D C0020
-----------------------------------------------------------------
keys in buffer |K2 |K1 | ??? | ? | Storage for B C0030
-----------------------------------------------------------------
keystrokes. K2 and K1 are pointers to beginning and end of C0040
-----------------------------------------------------------------
| Start of RSTK | 15 key buffer (2 nibbles per key) for C0050
-----------------------------------------------------------------
pointer | Start of stack | End of stack | End of RSTK C0060
-----------------------------------------------------------------
HOME (??) | Menu keys ptr | Internal loop ptr |Local variable C0070
-----------------------------------------------------------------
PC (copy of D0) | Ptr to HOME (??) | Ptr to cur. dir | Ptr to C0080
-----------------------------------------------------------------
| LAST arg2 ptr | LAST arg1 ptr | Note 1 | RPL C0090
-----------------------------------------------------------------
| Note 3 | Note 2 | LAST arg3 ptr | C00A0
-----------------------------------------------------------------
3 ptr | CMD line 2 ptr | CMD line 1 ptr | ????? C00B0
-----------------------------------------------------------------
Note 5 | Note 4 | CMD line 4 ptr | CMD line C00C0
-----------------------------------------------------------------
Free nibs / 5 | D0000 | Custom menu ptr | C00D0
-----------------------------------------------------------------
flags |PD | ????? | Last ERRN (?) | C00E0
-----------------------------------------------------------------
| | | Note 6 | | | | | | | Internal C00F0
-----------------------------------------------------------------
..1 | ANN | | | | | | | | | | | | | | C0100
-----------------------------------------------------------------
| | | | User flags 64.. C0110
-----------------------------------------------------------------
| | | | | | | | | | | | | | | | | C0120
-----------------------------------------------------------------
| | | | | | | | | | | | | | | | | C0130
-----------------------------------------------------------------
| | | | | | Last ERRN (?) | L | | | | C0140
-----------------------------------------------------------------
RPL | | ? |P2 |P1 |T1 | Menu3 | Menu2 | Menu1 | | C0150
-----------------------------------------------------------------
| | | | | | | | Note 7 | Ptr to current C0160
-----------------------------------------------------------------
Where:
CALIB FACTOR - Calibration factor that relates CPU clock to
real-time. Calculated by mcode routine at 01143
Note 1 - Contains RPL location to resume after garbage collection (?)
Note 2 - Points to a 336 bit binary integer. This integer is normally
the first object on the heap, at location C0184, but (?) if
its value has changed since the last garbage collection, it may
be elsewhere (pure conjecture)
Note 3 - This seems to point to a list { {} {} } which is located
at the boundary between objects allocated before/after the
last garbage collection
Note 4 - This seems to always contain 04075 - a pointer to a 0-bit
binary integer in ROM
Note 5 - This seems to always contain 04093 - a pointer to an empty
algebraic '' in ROM
PD - Print Display: This nibble is set to 1 when the ON-L key
combination is pressed, and is reset to 0 when the display
has finished printing.
Note 6 - This contains the number of nibbles on the stack (5 per level)
excluding the arguments for the current function
ANN - Current status of the annunciators
L - Number of arguments that were saved for recall by LAST
Menu1 - The menu currently display, 00 if cursor keys active
Menu2 - Offset into current menu (multiple of 6 in normal operation)
Menu3 - Menu that is current (not necessarily displayed), 00 if none
uses same numbering as MENU command
T1 - 10 minute counter for turning off inactive calculator
P1 - # of lines currently in printer's buffer (8 max)
P2 - Counter for print timing: counts 3 2 1 0, decrements P1
Note 7 - Saves the m-code address the garbage collection routine returns
to.
Complete memory map:
The structure of the rest of memory follows. I have tried to indicate
the locations that various system pointers point to by giving the address
of the system pointer and an arrow of sorts. Also, the standard uses of some
of the CPU registers are indicated (e.g. B(A) ---> The 5-nibble A-field of
register B points to the RPL return stack)
<--------- increasing addresses
|
----------------------------------------------------- |
Fixed system | | : C0000 |
storage | See above description | v
| |
-----------------------------------------------------
| /------------[C00A5]
HEAP | 00064 .. 336-bit binary .. 00059 02A70 U : C0183
|
|-------------------- SSSSS Object U
Objects in use at | ...
time of last garbage| ...
collection. SSSSS | /----SSSSS = size----\
is the size in nibs | SSSSS Object U
of entire object |
-------------------- /----[C00AA]
Divider | 0001A 02F90 04089 04089 02A96 U
--------------------
Objects allocated | SSSSS Object U
since last GC. The | ...
U nibble is a usage | ...
flag for GC routine | SSSSS Object U
-------------------------------
|
RPL return stack | {oldest return address} 00000 <--[C005A]
(RSTK) | rrrrr rrrrr rrrrr rrrrr
| {most recent return address}
| \-------------------------------[C005F], B(A)
| grows|
---------------------- |
| |
Free memory | v ...
5 * D(A) | ...
5 * [C00DC] | ^ ...
| |
---------------------- |
| grows|
Data stack | Level3 Level2 Level1 <--[C0064], D1
| ...
5 nibble pointer | 00000 {Highest Level}
for each level | \---------------------------[C0069]
----------------------
|
??? | ...
|
----------------------
Local variables | /--------SSSSS = frame size--------\
| binding ... binding TTTTT SSSSS <--[C006E]
Frame types: | \--------------frame type
0 - Normal | ...
1 - ????? | binding ... binding TTTTT SSSSS
2 - Stack save -----------------------------
Bindings are all ten nibbles, of the form | 00000
ddddd nnnnn : nnnnn points to name |
ddddd points to value |
(in special cases, ddddd is value) |
Sorry, but more details will have to wait |
for a separate article. |
-----------------------------------------------
Internal loop records |
(User loops are not | RecordN ... Record1 RRRRR <--[C0073]
handled here) -----------------
RRRRR = number of records |
Record = fffff ccccc 00000 |
final current (???) |
value value |
------------------------------------------
Menu Key data structure |
| NN W <--[C0078]
W = flags (indicates which | Name3 Name2 Name1
sections are available) | Name6 Name5 Name4
Structure to right |
assumes W = C | 04075 0407F
NN = number of entries per |
section |
Namex = Pointer to string, or | Func3 Func2 Func1
pointer to function | Func6 Func5 Func4
that creates string |
for menu key x | 00000 18F25 18F75
0407F-> "" 04075-> " " -----------------------
Funcx = Pointer to execution routine for menu key x |
18F25->??? 18F75->??? |
-----------------------------------------------------------
| object ... 02AB8 | : HOME <-[C007D],
User | | <-[C0087]
variables | ... 02AB8 ... |
| \---------------[C0082]
(Future article) | ... object ... | current dir
(???) | |
-----------------------------------------------------------
: D0000<-[C00D7]