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upd1771: Very small documentation update. no whatsnew.

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Jonathan Gevaryahu 2013-03-24 17:17:54 +00:00
parent bee34ea13e
commit 27d0492811
1 changed files with 3 additions and 4 deletions
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7
src/mess/audio/upd1771.c
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@ -80,8 +80,8 @@
L -> selector of left or right half of the ram word
?bits:
D (having to do with the DAC)
N (having to do with the pseudorandom noise interrupt, namely setting the clock divider ratio for the PRNG clock vs cpu clock)
MODE (enabling/disabling/acking the noise interrupt, and the tone interrupts (there are four!))
N (3 bits? having to do with the pseudorandom noise interrupt, namely setting the clock divider ratio for the PRNG clock vs cpu clock)
MODE (5 or more bits? enabling/disabling/acking the noise interrupt, and the tone interrupts (there are four!))
SP (the stack pointer, probably 5 bits, points to the stack ram; may encompass H and L as above!)
FLO: unsure. quite possibly 'flag overflow' used for branching. there likely exists other flags as well...
ODF: 'output data flag?', selects which half of a selected ram word is output to the dac not really sure of this?
@ -145,8 +145,7 @@
(NOTE: the photomicrograph in the bristow book makes it fairly clear due to
pad thicknessess that the real VCC is pin 8 and the real GND is pin 14.
Pins 16 and 17 are some sort of ?mode? inputs but could be the /EXTINT pin too?
Pin 15 MIGHT be the reset pin or could be a TEST pin. RESET could also be pin 7.)
The function of pin 7 is unknown.
Pins 11 and 13 go to a special circuit, which according to kevtris's analysis
of my schematics, consist of a balanced output (not unlike XLR cables),