The PDP-6/10 instruction set may seem daunting at first, but it is actually very regular and easy to understand. You can even completely memorize it without too much effort if you understand how it works.
You can find a description of the PDP-6/10 instruction here for the PDP-6 (src), KA10 (src).
You can find tables of all PDP-6/10 instructions (and monitor UUOs) here for the PDP-6 (src), KA10 (src), KI10 (src), KL10 (src).
See this table for a description of the single bits of the PDP-6 instructions:
UUO
000 XXX XXX
FSC 132
bytes
001 011 XXX
XXX: 011 - IBP (CAO)
100 - ILDB (LDCI)
101 - LDB (LDC)
110 - IDPB (DPCI)
111 - DPB (DPC)
floating point
(FAD|FSB|FMP|FDV)R?[LMB]?
001 1XX YZZ
XX: 00 - FAD
01 - FSB
10 - FMP
11 - FDV
Y: round
ZZ: 00
01 - (L) two ACs
10 - (M) memory
11 - (B) both
full word
MOV[ESNM][IMS]?
010 00X XYY
XX: 00 - MOVE
01 - MOVS
10 - MOVN
11 - MOVM
YY: 00
01 - (I) immediate
10 - (M) memory
11 - (S) self
multiply/divide
I?(MUL|DIV)[IMB]?
010 01X YZZ
X: 0 - MUL
1 - DIV
Y: 0 - (I-) one AC
1 - two ACs
ZZ: 00
01 - (I) immediate
10 - (M) memory
11 - (B) both
shifts
(ASH|ROT|LSH)C?
010 100 XYY
X: (C) combine two ACs
YY: 00 - ASH
01 - ROT
10 - LSH
11 - unassigned
misc
010 101 XXX
XXX: 000 - EXCH
001 - BLT
010 - AOBJP
011 - AOBJN
100 - JRST
101 - JFCL
110 - XCT
111 - unassigned
jump/push down
010 110 XXX
XXX: 000 - PUSHJ
001 - PUSH
010 - POP
011 - POPJ
100 - JSR
101 - JSP
110 - JSA
111 - JRA
add/subtract
(ADD|SUB)[IMB]?
010 111 XYY
X: 0 - ADD
1 - SUB
YY: 00
01 - (I) immediate
10 - (M) memory
11 - (B) both
jump/skip
(CA[IM]|JUMP|SKIP|AO[JS]|SO[JS])(L|E|LE|A|GE|N|G)?
011 VVW XYZ
VV: 00 - CAI/CAM (ACCP)
01 - JUMP/SKIP (MEMAC TST)
10 - AOJ/AOS (MEMAC + 1)
11 - SOJ/SOS (MEMAC - 1)
W: 0 - (I) immediate / (J) AC-JUMP
1 - (M) memory / (S) MEM-SKIP
X: negate condition YZ
Y: skip/jump on =
Z: skip/jump on <
boolean
(SETZ|AND|ANDCA|SETM|ANDCM|SETA|XOR|IOR|
ANDCB|EQV|SETCA|ORCA|SETCM|ORCM|ORCB|SETO)[IMB]?
100 ABC DXX
ABCD: truth table for AC and MEM
M
| 0 1
--+----
0| A C
A |
1| B D
0001 - AND / ORCB - 1110
0010 - ANDCA / ORCM - 1101
0100 - ANDCM / ORCA - 1011
0000 - SETZ / SETO - 1111
0011 - SETM / SETCM - 1100
0101 - SETA / SETCA - 1010
0110 - XOR / EQV - 1001
0111 - IOR / ANDCB - 1000
XX: 00
01 - (I) immediate
10 - (M) memory
11 - (B) both
half word
H[LR][LR][ZOE]?[IMS]?
101 WXX YZZ
W: 0 - dest L
1 - dest R
XX: 00
01 - (Z) zero other half
10 - (O) set other half to ones
11 - (E) sign extend other half
Y: swap source halves
ZZ: 00
01 - (I) immediate
10 - (M) memory
11 - (S) self
logical test and modify
T[RLDS][NZCO][EAN]?
110 UVW XYZ
U: complement masked bits after V
V: 0 - (N) do nothing with masked bits / (C)
1 - (Z) zero masked bits / (O)
W: 0 - (R/L) immediate
1 - (D/S) memory
X: negate condition Y
Y: 0 - skip never / (A)
1 - (E) skip if zero / (N)
Z: swap mask halves
IO
111 XXX XXX XYY Y
XXX XXX X: device code
YYY: 000 - BLKI
001 - DATAI
010 - BLKO
011 - DATAO
100 - CONO
101 - CONI
110 - CONSZ
111 - CONSO