[Premium-Rx] RA6790 / RA1792 processor board details

[Greg W. Bailey]

Fellow members:

I have received this from a non-member and am forwarding it to the List unmodified-

Greg

----- Original Message ----- 
From: "Küppers" 
To: premium-rx-owner at ml.skirrow.org 
Sent: Tuesday, February 03, 2004 1:23 PM
Subject: RA6790 / RA1792 processor board details


Hello, 

although I have not subscribed to the Premium-RX list, I hope the following gets through as your members might be interested in the following points concerning the RA1792/RA6790 A6A2 processor boards. 

Procuring MK3850/3853 replacements: 
If you are in need of replacements for the 3850 and 3853 chips, then you might consider going to Ebay and bidding for a "Chess Champion MK I". This is a 1970's chess computer made by NOVAG. There is an MK3850 and a 3853 inside, both are mounted on sockets. The Chess Champion MK I is auctioned quite frequently, I just got one for 11 EURO. 

RA1792 1 Hz frequency resolution rom patches: 
See below for patches to the 3 chips eprom version P83040/ISS 1 8204, which will allow 1 Hz tuning resolution and display: 

P83040/1/A: Address original value -> new value 
(U5)          0x50f:          0x14 -> 0x2b 
              0x510:          0x14 -> 0x2b 

P83040/2/A:   0x398:          0x22 -> 0x2b 
(U6)          0x399:          0x0f -> 0x2b 

P83040/3/A:   0x10e:          0x70 -> 0x2b 
(U7)          0x760:          0x76 -> 0x67 
              0x762:          0xf6 -> 0xff 

The original program already calculates frequencies with 1 Hz accuracy, but sets the 1 Hz digit to 0 when transfering it to the synthesizer board, and blanks it when transfering data to the 
display. I NOPed the relevant bytes and also modified the smallest frequency step size to be 1 Hz instead of 10 Hz. 

If there is interest, I can provide the patched rom images. The P83040 roms are what I found in my receiver, which is marked DRG. No ST80730, GA/S2/0/0/0/A, Ser.-No. 9330. 

Best regards 
Guido Kueppers 
(df2kw) 

kueppersmclaudius17 at t-online.de 



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