+Atari2600PAL Posted January 26 Share Posted January 26 I've been populating my PEB with various cards (like SAMS, RS232, P-Code, TIPI, Speech, FDC) and I understand how to use them and how they work (at the user level) and have an FG99/F18A, but am struggling with understanding things at the GROM/Addressing level I get what GROMs are, but not the whole addressing structure of the TI, if you get my meaning. I'm shortly going to be adding an HSGPL card to my PEB to play around with, but the manual assumes you already know everything about the internal structure of the TI and statements like below make my blood run cold I was wondering if anyone could point me to a "TI ROM/GROM/Addressing for Dummies" please? Something that will help me understand how it all hangs together (I've read the FAQ BTW) Many thanks Quote Link to comment Share on other sites More sharing options...
HOME AUTOMATION Posted January 26 Share Posted January 26 "Copy ROM 1 to 3?" ...If you don't eat yer meat, you can't have any pudding🍮 "Copy ROM 0+1?" ...How can you have any pudding if you don't eat yer meat?🍖 ...All in all... 🚲👨 1 Quote Link to comment Share on other sites More sharing options...
HOME AUTOMATION Posted January 26 Share Posted January 26 There's this... Q: What can I do, if Bank0 becomes corrupt and I can't boot? A: There is a trick if you have damaged the first banks: exchange the FLASH-EPROMs which contain the GROMs, so you will exchange banks 8 and 0, 9 and 1 etc..... Then you can start the system and repair the damaged banks, which resist now at the second half (from 8... on 16bank-cards.) TI made a mistake in the ROM-0, some code from GROM-0 is accessed via >9804, the second bank instead of the base-bank, so if you change the GROM-0, do it always in both banks (minimum!), without going through the main-screeen (power-up) between this!!! {otherwise you have to do the procedure as described above...{grin}} ...excerpt from... System 99 Users Group (SNUG) * HARDWARE HELP FILE * Version: 07.09.2000 More stuff in parent directory: https://ftp.whtech.com/datasheets and manuals/Hardware/SNUG/ Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 Hi @HOME AUTOMATION Thanks for the info It's not really the HSGPL card in particular I'm trying to learn currently, it's how the whole TI addressing is structured in the console and how rom/grom/gram fit in to all this A TI 101 if you like Thanks Quote Link to comment Share on other sites More sharing options...
HOME AUTOMATION Posted January 26 Share Posted January 26 One of the best... The TI-99/4A Tech Pages ...I always liked the Memory Maps, in the back of the MINI MEMORY guide! Mini Memory by Texas Instruments ...though they don't cover GROM. 1 Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 22 minutes ago, HOME AUTOMATION said: One of the best... The TI-99/4A Tech Pages ...I always liked the Memory Maps, in the back of the MINI MEMORY guide! Mini Memory by Texas Instruments ...though they don't cover GROM. Many thanks, will have a read Quote Link to comment Share on other sites More sharing options...
HOME AUTOMATION Posted January 26 Share Posted January 26 Don't miss this... Disabling the GROMs Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 18 minutes ago, HOME AUTOMATION said: Don't miss this... Disabling the GROMs Thanks! Quote Link to comment Share on other sites More sharing options...
RXB Posted January 26 Share Posted January 26 (edited) 2 hours ago, Atari2600PAL said: I've been populating my PEB with various cards (like SAMS, RS232, P-Code, TIPI, Speech, FDC) and I understand how to use them and how they work (at the user level) and have an FG99/F18A, but am struggling with understanding things at the GROM/Addressing level I get what GROMs are, but not the whole addressing structure of the TI, if you get my meaning. I'm shortly going to be adding an HSGPL card to my PEB to play around with, but the manual assumes you already know everything about the internal structure of the TI and statements like below make my blood run cold I was wondering if anyone could point me to a "TI ROM/GROM/Addressing for Dummies" please? Something that will help me understand how it all hangs together (I've read the FAQ BTW) Many thanks You need my GPL HOW 2 Series I also include Asssembler, Disassembler, Linker and manuals. Edited January 26 by RXB Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 Thanks @RXB will take a look 1 Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted January 26 Share Posted January 26 Here is some basic info. Certainly more in those refs, starting with Thierry's TI Tech Pages: GROM GROM is a separate memory space, organized as 8 banks at 8K boundaries. To access GROM, you first load an address counter, then read from a a data port. It's very similar to VDP memory access. GROM chips have a starting address burned in. When you set the address counter from 0000-FFFF, each GROM chip compares the address. Only a GROM chip which matches that address becomes active. Memory Map of GROM 0000 17FF GROM 0 console 2000 37FF GROM 1 console 4000 57FF GROM 2 console 6000 77FF GROM 3 expansion: cartridge port or P-BOX card .. E000 F7FF GROM 7 expansion The console reserves GROM 0,1,2 for the "GPL Operating System". Cartridges or P-Box cards can provide GROM 3-7 without conflicting with the console. The next byte you read will come from that chip at that address. Each time you read a byte, the GROM advances its address counter. GROM Base GRMRD EQU >9800 to read a byte of data GRMWA EQU >9C02 to set the address >9800 is called the "GROM Base" in the 99/4A CPU Memory Map. More about GROM base later. (Hint: >9804 is for an expansion bank, >9820 is Gram Karte expansion bank...) Contrast the memory-mapped GROM ports to the VDP ports: GRMRD EQU >9800 to read a byte of data GRMRA EQU >9802 to retrieve the address, plus 1 GRMWD EQU >9C00 to write data - useless for GROM chips GRMWA EQU >9C02 to write address VDPRD EQU >8800 to read a byte of data VDPSTA EQU >8802 to retrieve the STATUS REGISTER VDPWD EQU >8C00 to write data VDPWA EQU >8C02 to write address Code This code copies char defs from GROM to VDP. (This is the only code I've ever written to access GROM) SETGWA SWPB R0 least significant byte goes first MOVB R0,*R15 SWPB R0 MOVB R0,*R15 RT SETVWA SWPB R0 least significant byte goes first MOVB R0,@VDPWA SWPB R0 MOVB R0,@VDPWA RT CHARA1 EQU >06B4 pretend this is the part of GROM 0 with the ordinary character definitions * Copy uppercase character set from GROM to VDP START LI R15,GRMWA GPL keeps its GRMWA at >83FE, which is R15 of GPLWS >83E0 LI R0,CHARA1 BL @SETGWA set the address from R0 (for GROM base relative to R15) PATTBL EQU >0800 assume the VDP pattern table is at >800 LI R0,PATTBL+>200 address for char 64: @ABC ... (NOTE 1) BL @SETVWA LI R2,>100 loop counter: 32 chars of 8 bytes LOOP MOVB @GRMRD,@VDPWD alternately: MOVB ->402(R15),@VDPWD DEC R2 JNE LOOP ... Unlike VDP, you can read back the GROM address. A subroutine exit would restore this previous value minus 1. GROM has already added 1 to it. Expanded GROM bases >9800 is called the "GROM Base" in the 99/4A CPU Memory Map. Add 4 to the port addresses to access GROM expansion banks. / GRMRD2 EQU >9804 to read from active GROM in BANK 2 The console checks BANK 2 for valid GROMs. If it finds any, it presents REVIEW MODULE LIBRARY as an option after the title screen. Selecting that will change the GROM base and show what's in it. (I've seen this message by accident, but never had any actual GROM expansion.) Overriding Console GROM I have no knowledge of GRAM cards for the P-Box, but I know this statement from Peripheral Expansion Box Technical Data (and other books). "The GROM chips are poor drivers at best", which implies that another peripheral can be built to override the built-in console GROMs. So if your GRAM KARTE or HSGPL is configured to override console GROM 0, and it's messed up, you won't be able to start up at all. The comment from @GDMike about >9804 .. because of this bug, the console sometimes reads from GROM 8 when it should read GROM 0. Inside the console it goes to GROM 0 anyway. * Note: TI BASIC character bias TI BASIC plays a trick by translating ASCII >20 (space) to char >80 etc. BASIC does this trick to more tightly pack VDP RAM. This is why a PAB structure has a byte "BASIC character bias" of >60. If DSRs put any text on the screen, they need to add the bias to each ASCII code. See TI BASIC VDP Memory Map 2 Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 Many thanks @FarmerPotato very interesting read, much appreciated Before I do anything else I need to fix the keyboard on my main TI as when I powered it up I've found the matrix pin 1 isn't working (none of the characters on that pin will function) Took it apart to check the connector and all looks fine, but I reseated it and put it back together (not fun because of the way I've attached the F18a VGA socket) and still doesn't work I have a spare keyboard, but IIRC that's faulty, so next job is to dismantle my spare TI as a keyboard donor (am hoping it's just the keyboard anyway) Quote Link to comment Share on other sites More sharing options...
Gary from OPA Posted January 26 Share Posted January 26 @Atari2600PAL could be an issue with the TMS9901 if you still have issues with another keyboard. Sadly, the 9901 chip is one of the more weaker TI chips, has a bad habit of breaking down for the smallest thing. Check it's socket and pins remove any corrosion. Quote Link to comment Share on other sites More sharing options...
RickyDean Posted January 26 Share Posted January 26 53 minutes ago, Atari2600PAL said: Many thanks @FarmerPotato very interesting read, much appreciated Before I do anything else I need to fix the keyboard on my main TI as when I powered it up I've found the matrix pin 1 isn't working (none of the characters on that pin will function) Took it apart to check the connector and all looks fine, but I reseated it and put it back together (not fun because of the way I've attached the F18a VGA socket) and still doesn't work I have a spare keyboard, but IIRC that's faulty, so next job is to dismantle my spare TI as a keyboard donor (am hoping it's just the keyboard anyway) You do have some possible solutions too, Such as Fred Kaal's https://hexbus.com/ti99geek/Projects/kbti994a/kbti994a.html usb keyboard solution or Jedimatt's https://www.jedimatt42.com/4a/ti99usbkeys, if it's not a bad 9901, and you can't fix the keyboard otherwise. FYI Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 Thanks @Gary from OPA & @RickyDean I'm happy to say the replacement keyboard has fixed the problem! Sometime I'll fit the faulty keyboard in the spare machine to double-check it's faulty and not a bad connection 2 Quote Link to comment Share on other sites More sharing options...
RickyDean Posted January 26 Share Posted January 26 39 minutes ago, Atari2600PAL said: Thanks @Gary from OPA & @RickyDean I'm happy to say the replacement keyboard has fixed the problem! Sometime I'll fit the faulty keyboard in the spare machine to double-check it's faulty and not a bad connection Good, I would check the wire harness on that pin to see if you have continuity. Those internal wires can break easily if someone was rough on removing the keyboard in the past. 1 Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 1 minute ago, RickyDean said: Good, I would check the wire harness on that pin to see if you have continuity. Those internal wires can break easily if someone was rough on removing the keyboard in the past. Will do, thanks 1 Quote Link to comment Share on other sites More sharing options...
+Atari2600PAL Posted January 26 Author Share Posted January 26 36 minutes ago, RickyDean said: Good, I would check the wire harness on that pin to see if you have continuity. Those internal wires can break easily if someone was rough on removing the keyboard in the past. Bingo! Strangely the cable I thought was broken (pin 1) did have continuity but a couple of others didn't And then the whole ribbon cable parted from the circuit board in my hand… When I have time I’ll try to fit a new ribbon Thanks 3 1 Quote Link to comment Share on other sites More sharing options...
+Lee Stewart Posted January 26 Share Posted January 26 4 hours ago, RickyDean said: Good, I would check the wire harness on that pin to see if you have continuity. Those internal wires can break easily if someone was rough on removing the keyboard in the past. Yeah—that harness is stiff. I have taken the keyboard out; fixed the bad wire; re-assembled, only to break another wire. replacing that with a flexible cable is the only way to sanity! ...lee 3 1 Quote Link to comment Share on other sites More sharing options...
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