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Good day.

I'm reversing an automotive ECU firmware which works on SAF80-C509 processor (Intel 51 architecture). Now, I've got this part of code:

code:64C5                 mov     MD0, R0         ; Multiplication/Division Register 0
code:64C7                 mov     MD1, R1         ; Multiplication/Division Register 1
code:64C9                 mov     MD4, #0A0h      ; Multiplication/Division Register 4
code:64CC                 mov     MD5, #0         ; Multiplication/Division Register 5
code:64CF                 nop
code:64D0                 nop
code:64D1                 nop
code:64D2                 nop
code:64D3                 mov     B, MD0          ; Quot = A:B
code:64D6                 mov     A, MD1          ; Multiplication/Division Register 1
code:64D8                 mov     R2, MD2         ; Multiplication/Division Register 2
code:64DA                 mov     R2, MD3         ; spare Reminder

According to specification, the write sequence MD0, MD1, MD4, MD5 means that it's 16bit/16bit division operation. At the same time, the result should be in MD1:MD0 for quotient (High:Low) and in MD5:MD4 in reminder. As one can see, the firmware reads MD1:MD0 and MD3:MD2. An obvious discrepancy. As far as I understand, if MD5 isn't read, then read sequence isn't over and it may lead to some error condition.

I've seen some issues (typos) in the specification I've got. Hence, here is my question: is it a typo in the specification again?

P.S.: I've got this specification (user manual) from Keil site: https://www.keil.com/dd/docs/datashts/infineon/c509_um.pdf

Screenshot from specification

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