HuCard pinout

Pinout

Card |  | PC Engine
-----+--+--------------------------
   1 |->| /CD
   2 |->| AUDIO IN
   3 |<-| CPU PA19
   4 |<-| CPU PA16
   5 |<-| CPU PA15
   6 |<-| CPU PA12
   7 |<-| CPU PA7
   8 |<-| CPU PA6
   9 |<-| CPU PA5
  10 |<-| CPU PA4
  11 |<-| CPU PA3
  12 |<-| CPU PA2
  13 |<-| CPU PA1
  14 |<-| CPU PA0
  15 |<>| CPU D0 (PCE) or D7 (TG16)
  16 |<>| CPU D1 (PCE) or D6 (TG16)
  17 |<>| CPU D2 (PCE) or D5 (TG16)
  18 |--| GND
  19 |<>| CPU D3 (PCE) or D4 (TG16)
  20 |<>| CPU D4 (PCE) or D3 (TG16)
  21 |<>| CPU D5 (PCE) or D2 (TG16)
  22 |<>| CPU D6 (PCE) or D1 (TG16)    
  23 |<>| CPU D7 (PCE) or D0 (TG16)    Orientation:
  24 |<-| CPU PA20                     --------------------------
  25 |<-| CPU PA10                     .-------------------.
  26 |<-| CPU /RD                      | .---------..------|
  27 |<-| CPU PA11                     | |         ||      |- 1
  28 |<-| CPU PA9                      |>|  Label  ||      |
  29 |<-| CPU PA8                      | |         ||      |- 38
  30 |<-| CPU PA13                     | '---------''------|
  31 |<-| CPU PA14                     '-------------------'
  32 |<-| CPU PA17
  33 |<-| CPU PA18                     Legend: 
  34 |<-| CPU /WR                      --------------------------
  35 |<-| HSM                          [HuCard]-- Power, n/a  
  36 |<-| /RST                         [HuCard]<- HuCard input 
  37 |->| /IRQ2                        [HuCard]-> HuCard output 
  38 |--| +5V                          [HuCard]<> Bidirectional

Signal descriptions

• /CD: Card detect. Connects to the expansion port. Grounded by the HuCard so the CD-ROM² can tell a card is inserted.
• AUDIO IN: Mono audio. Mixed into both channels.
• CPU PA20..0: CPU physical address (the 21-bit post-MMU address). PA20 is used as /CE.
• CPU D7..0: The order of these pins depends on region. For PC Engine, they are ascending, and for TurboGrafx-16, they are descending.
• HSM: High speed mode, asserted by the CPU when operating at 7.16 MHz.