CPU pinout

Pinout
^                                          / \                                          /   \                                         /     \                             CPU PA5 <- / 1  80 \ -> CPU PA6 CPU PA4 <- / 2   79 \ -> CPU PA7 CPU PA3 <- / 3     78 \ -> CPU PA8 CPU PA2 <- / 4   O   77 \ -> CPU PA9 CPU PA1 <- / 5         76 \ -- +5V (VBB) CPU PA0 <- / 6           75 \ -- GND (VSS2) GND (VSS1) -- / 7             74 \ -> CPU PA10 +5V (VAA) -- / 8               73 \ -> CPU PA11 n/c ?? / 9                 72 \ -> CPU PA12 OSC -> / 10                  71 \ -> CPU PA13 /RST -> / 11                    70 \ -> CPU PA14 RDY -> / 12                      69 \ -> CPU PA15 SX <- / 13                        68 \ -> CPU PA16 HSM <- / 14                          67 \ -> CPU PA17 +5V (VPPD) -- / 15                            66 \ -> CPU PA18 GND (VSS5) -- / 16                              65 \ -> CPU PA19 AUDIO LOUT <- / 17                                   \ AUDIO ROUT <- / 18                                    / +5V AUDIO (VPPA) -- / 19                                 64 / -> CPU PA20 GND AUDIO (AGND) -- / 20                                 63 / -> CPU /WR GND (VSSA) -- / 21         HuC6280 HUDSON          62 / -> CPU /RD K0 -> / 22         Package QFP-80          61 / -> /CER n/c ?? / 23                                 60 / -> /CE7 K1 -> / 24                                 59 / -> /CEK /                                    58 / -- GND (VSS3) \                                   57 / -- +5V (VCC) K2 -> \ 25                              56 / <> CPU D7            K3 -> \ 26                             55 / <> CPU D6          Orientation: K4 -> \ 27                          54 / <> CPU D5                         K5 -> \ 28                         53 / <> CPU D4               64         41 K6 -> \ 29                      52 / <> CPU D3                 |         | K7 -> \ 30                    51 / <> CPU D2                 .---. O0 <- \ 31                  50 / <> CPU D1               65-|          O|-40 O1 <- \ 32                49 / <> CPU D0                   |    HuC6280| O2 <- \ 33              48 / -- GND (VSS4)             80-|O  HUDSON  |-25 O3 <- \ 34            47 / -- +5V (VDD)                  '---' O4 <- \ 35          46 / -> SYNC                         |         | O5 <- \ 36        45 / <- /NMI                         01         24 O6 <- \ 37  O   44 / <- /IRQ1 O7 <- \ 38    43 / <- /IRQ2                       Legend: /EAT -> \ 39  42 / <- /EA1 /EA3 -> \ 40 41 / <- /EA2                         --[HuC6280]-- Power, n/a \    /                                   ->[HuC6280]<- HuC6280 input \  /                                    <-[HuC6280]-> HuC6280 output \ /                                    <>[HuC6280]<> Bidirectional V                                     ??[HuC6280]?? Unknown

Signal descriptions

 * OSC: 21.4772 MHz clock input.
 * SX: An inverted output of the system clock, normally not connected.
 * CPU PA20..0: CPU physical address. PA12..0 come from the 65C02 core's A12..0 and PA20..13 from the MMU, selected by the 65C02 core's A15..13.
 * K7..0: General-purpose input (GPI) mapped to $FF:$1000-$13FF read.
 * O7..0: General-purpose output (GPO) mapped to $FF:$1000-$13FF write.
 * /CER: RAM chip enable. Asserted when accessing banks $F8-$FB.
 * /CE7: HuC6270 chip enable. Asserted when accessing $FF:$0000-$03FF
 * /CEK: HuC6260 chip enable. Asserted when accessing $FF:$0400-$07FF
 * /EAT, /EAT3..1: CPU test inputs. EAT is a timer for the U-bus (HuC6280 internal peripheral bus).
 * HSM: High speed mode. Asserted if the CPU is running in its 7.16 MHz mode.
 * /IRQ1: Interrupt input from the VDC.
 * /IRQ2: Interrupt input from HuCards and the expansion port.
 * /NMI: Non-maskable input from the expansion port.
 * SYNC: Asserted during opcode fetch and deasserted otherwise (including during reset). Can be used for single-stepping execution, but is normally not connected.
 * RDY: Ready. Deasserting halts the CPU until asserted again.
 * /RST: Reset.