VRC7 pinout
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Konami VRC7: 48-pin 0.6" PDIP marked: "VRC VII 053982" (canonically iNES Mapper 085)
.---\/---.
PPU /RD -> | 01 48 | -> NC
PPU A13 -> | 02 47 | <- M2
GND -- | 03 46 | -> WRAM /CS
R/W -> | 04 45 | <- /ROMSEL
/IRQ <+ | 05 44 | -> PRG /CS
CIRAM A10 <- | 06 43 | -> Audio Out
CPU D0 <> | 07 42 | -- +5V
CPU D1 <> | 08 41 | -> CHR A17
CPU D2 <> | 09 40 | -> CHR A16
CPU D3 <> | 10 39 | -> CHR A15
CPU D4 <> | 11 38 | -> CHR A14
CPU D5 <> | 12 37 | -> CHR A13
CPU D6 <> | 13 36 | -> CHR A12
CPU D7 <> | 14 35 | -> CHR A11
/DEBUG -> | 15 34 | -> CHR A10
CPU A5 -> | 16 33 | <- PPU A12
Crystal X2 -> | 17 32 | <- PPU A11
Crystal X1 <- | 18 31 | <- PPU A10
CPU An -> | 19 30 | -- +5V
PRG A13 <- | 20 29 | <- CPU A14
PRG A14 <- | 21 28 | <- CPU A13
PRG A15 <- | 22 27 | <- CPU A12
PRG A16 <- | 23 26 | -> PRG A18
GND -- | 24 25 | -> PRG A17
`--------'
01,02: this doesn't make sense;
the VRC7 provides none of extra nametables, control of CIRAM /CE, nor CHR /CE.
Pin 48 appears to be derived from pin1 and pin2.
If it was {pin1 OR pin2}, i.e. CHR /CE, it could be used for a 28-pin CHR ROM, but why didn't TTA2 use it?
17,18: missing on TTA2, 3.58MHz ceramic resonator on LP
19: A3 on TTA2, A4 on LP
Expansion audio mixing circuit:[1]
The audio is mixed through a ceramic daughterboard with a 9 pin SIP connector. Pins 4-6 are unconnected,
since they were primarily used for laser trimming the resistors during production.
From 2A03---o--+-----------+
(Cart.45) | |
To RF-------o--| |
(Cart.46) | |
GND---------o--| |
| |
NC o--| |
(Mix.4) | |
NC o--| |
(Mix.5) | |
NC o--| |
(Mix.6) | |
GND---------o--| |
| |
From VRC7---o--| |
(VRC7.43) | |
VCC---------o--+-----------+
Equivalent circuit schematic:
The daughterboard uses a dual op-amp for amplification. Only one amplifier is used.
From 2A03----------------------------------------------------/\/\/---+
(Cart.45) _ 3.9K |
| \ |
From VRC7---+---/\/\/---+--------+----------------|+ \ |
(VRC7.43) / 27K | / |IC.A>-+---/\/\/---+---To RF
\ --- \ +--|- / | 2.2K (Cart.46)
/ 2.2K --- 4.7n / 33K | |_/ |
| | | | 240K |
+-----------+--------+ NC------+--/\/\/--+
| (Mix.5) / |
| VCC---+-------+ \ |
| | _ | | / 4.3K |
| | | \| | NC------+ +---NC
| +-|+ \ --- (Mix.6) | / (Mix.4)
| | |IC.B>--x --- 0.1u --- \
| +-|- / | --- 0.22u / 910
| |_/| | | |
GND---------+-------+-------+------------------+---------+
Note that "DEBUG" mode is not function compatible with the default way the VRC7 is wired; nukeykt says that “in debug mode VRC7 changes its pinout: Pin 4 -> /CS, Pin 27 -> /IC, Pin 28 -> /WE, Pin 19 -> A0. Also at least pins 2 and 47 somehow affect debug mode”
See also:
- Decap'ed VRC7: https://siliconpr0n.org/archive/doku.php?id=digshadow:konami:vrc_vii_053982
- Quietust's annotations for the above decap: https://www.qmtpro.com/~nes/chipimages/#vrc7
- More commentary on VRC7 DEBUG mode: https://siliconpr0n.org/archive/doku.php?id=vendor:yamaha:opl2#vrc7_debug_mode
