Looking for info on pin 21 (ALPHA LOCK) use and the CRU

[jschultzpedersen]

I have been looking into reading and writing to pins to get access to the keyboard directly via the CRU. I think I get it. But one key has left me a bit unsure. That is the ALPHA LOCk mapped to pin 21. I saw a working example (see below) that loops until the key is pressed down. That is fine, and it works. But I have seen no documentation telling me why pin 7 is the pin to test. Neither the E/A manual nor the nouspikel.com docs mention this, as far as I can see. So where can I find such information?

       DEF  START                                                               
START                                                                           
       CLR  R12                                                                 
       SBZ  21                                                                  
L1     TB   7                                                                   
       JNE  L1                                                                  
       SBO  21                                                                  
       B    *R11                                                                                                                                
       END  

[Artoj]

I have been working on this diagram on and off for a while, I hope this helps.

 

[Asmusr]

2 hours ago, jschultzpedersen said:

I have been looking into reading and writing to pins to get access to the keyboard directly via the CRU. I think I get it. But one key has left me a bit unsure. That is the ALPHA LOCk mapped to pin 21. I saw a working example (see below) that loops until the key is pressed down. That is fine, and it works. But I have seen no documentation telling me why pin 7 is the pin to test. Neither the E/A manual nor the nouspikel.com docs mention this, as far as I can see. So where can I find such information?

       DEF  START                                                               
START                                                                           
       CLR  R12                                                                 
       SBZ  21                                                                  
L1     TB   7                                                                   
       JNE  L1                                                                  
       SBO  21                                                                  
       B    *R11                                                                                                                                
       END  

Did you see this? https://www.unige.ch/medecine/nouspikel/ti99/keyboard.htm#CRU map

 

Quote

The alpha-lock key is activated by the TMS9901 output P5 (R12 address >002A, bit 21) and reads together with keyboard row 4 (R12 = >000E, bit 7). This has the very unfortunate effect of messing up the joystick "up" signal when the alpha-lock key is engaged. Why the TI engineers did not pick row 7 (pin #11) instead, is a mystery to me.

 

Edited September 6 by Asmusr

[+jedimatt42]

It is documented as Cru R12 address 0x000E, but your code is using R12 set to 0. TB parameter is shifted left 1 and then added to the R12 value. 0x000E is 14. 7 shifted left 1 is 14, added to your crubase of 0 is 14... 

[jschultzpedersen]

The link to the keyboard article was just what I needed. Thanks a lot! I was led astray by the article on the TMS9901 Programmable systems interface where the CRU map of keys mapping of the TMS9901 does not mention the ALPHA LOCK. So I never looked further among the articles on nouspikel's site. Doh!