MV1A PALs

The MV1A MVS boards have two [PAL] PAL20V8H-15 chips which are used to provide some of NEO-C1's functions. If any of them fails, the board certainly won't start up.

They can be replaced with new or working chips programmed with the following JEDEC files:

SNK1A

Does some address decoding. Pin 1 might be AS instead of RW.

JEDEC file: File:SNK1A.zip

• /VPA = /i1 & A20 & A21 & A22I & A23I (Access Fxxxxx, interrupt ack cycle, signal 68k that we need an autovectored interrupt)
• /WRAMCS = /i1 & A20 & /A21 & /A22I & /A23I (Access 1xxxxx, work RAM)
• /o17 = /i1 & A20 & /A22I + /i1 & /A22I & A23I + /i1 & A22I & /A23I (Access x0x1 or 10xx (8xxxxx-Bxxxxx) or 01xx (4xxxxx-7xxxxx))
• /o18 = /i1 & A20 & /A21 & A22I & A23I (Access Dxxxxx, backup RAM)
• /DIPRD0 = /i1 & /A17 & /A18 & /A19 & A20 & A21 & /A22I & /A23I & /MGA53 & MGA52 (Read 0011000x, must be 300000-31FFFF LDS)
• /IN3 = /i1 & A17 & /A18 & /A19 & A20 & A21 & /A22I & /A23I & /MGA53 & MGA52 (Read 0011001x...)
• /o21 = /i1 & A17 & /A18 & /A19 & A20 & A21 & /A22I & /A23I & /MGA51 & MGA52 (Read 0011001x...)
• /SDW = /i1 & A17 & /A18 & /A19 & A20 & A21 & /A22I & /A23I & MGA51 & /MGA52 (Write 0011001x, must be 320000-33FFFE UDS)

SNK1B

Generates the DTACK signal.

JEDEC file: File:SNK1B.zip

• o17 = /i5 & rf21 + /i5 & i11 + /i6 & rf21 & i23 + /i6 & i14 & rf22 + /i6 & i14 & i23 + /i2 & /i6 & /i14 & /i23
• DTACK = i3 & i7 & i8 & i9 & i10 & /o17 & /rf21 + i3 & i4 & i7 & i8 & i9 & i10 & /o17
• /rf20 = i4 & i5 & i6
• /rf21 = i4 & i5 & i6 + /rf20
• /rf22 = /rf21 + i4 & i5 & i6