8251
Universal asynchronous receiver/transmitter.
+-----+--+-----+
D2 |1 +--+ 28| D1
D3 |2 27| D0
RxD |3 26| VCC
GND |4 25| /RxC
D4 |5 24| /DTR
D5 |6 23| /RTS
D6 |7 8251 22| /DSR
D7 |8 21| RST
/TxC |9 20| CLK
/WR |10 19| TxD
/CE |11 18| TxEMPTY
C//D |12 17| /CTS
/RD |13 16| SYCDET BD
RxRDY |14 15| TXRDY
+--------------+

8253, 8254
Programmable interval timer/counter.
+-----+--+-----+
D7 |1 +--+ 24| VCC
D6 |2 23| /WR
D5 |3 22| /RD
D4 |4 21| /CE
D3 |5 20| A1
D2 |6 8253 19| A0
D1 |7 8254 18| CLK2
D0 |8 17| OUT2
CLK0 |9 16| G2
OUT0 |10 15| CLK1
G0 |11 14| G1
GND |12 13| OUT1
+--------------+

8255
Parallel Peripheral Interface.
+-----+--+-----+
PA3 |1 +--+ 40| PA4
PA2 |2 39| PA5
PA1 |3 38| PA6
PA0 |4 37| PA7
/RD |5 36| /WR
/CE |6 35| RST
GND |7 34| D0
A1 |8 33| D1
A0 |9 32| D2
PC7 |10 8255 31| D3
PC6 |11 30| D4
PC5 |12 29| D5
PC4 |13 28| D6
PC0 |14 27| D7
PC1 |15 26| VCC
PC2 |16 25| PB7
PC3 |17 24| PB6
PB0 |18 23| PB5
PB1 |19 22| PB4
PB2 |20 21| PB3
+--------------+

Z8530, Z8531
Zilog Serial Communications Controller.
Z8531 has no synchronous capabilities.
+-----+--+-----+
D1 |1 +--+ 40| D0
D3 |2 39| D2
D5 |3 38| D4
D7 |4 37| D6
/INT |5 36| /RD
IEO |6 35| /WR
IEI |7 34| A0 A/B
/INTAK |8 33| /CE
VCC |9 32| A1 D/C
/W_REQA |10 Z8530 31| GND
/SYNCA |11 SCC 30| /W_REQB
/RTxCA |12 29| /SYNCB
RxDA |13 28| /RTxCB
/TRxCA |14 27| RxDB
TxDA |15 26| /TRxCB
/DTR_REQA |16 25| TxDB
/RTSA |17 24| /DTR_REQB
/CTSA |18 23| /RTSB
/DCDA |19 22| /CTSB
CLK |20 21| /DCDB
+--------------+

8574, 8574A
I2C parallel I/O expander.
I2C address is 0100xxx for the 8574 and 0111xxx for the 8574A, where xxx can be specified by the A0-2 inputs.
+---+--+---+
A0 |1 +--+ 16| VCC
A1 |2 15| SDA
A2 |3 14| SCL
P0 |4 13| /INT
P1 |5 8574 12| P7
P2 |6 11| P6
P3 |7 10| P5
GND |8 9| P4
+----------+

8584
I2C bus controller.
Bus controller ties to either Z80-style bus or to 68000-style bus, and determines the mode from the first few cycles.
+---+--+---+
CLK |1 +--+ 20| VCC
SDAo SDA |2 19| /RST /STB
SCLo SCL |3 18| /WR R//W
SDAi /IACK |4 17| /CS
SCLi /INT |5 16| /RD /DTACK
A0 |6 8584 15| D7
D0 |7 14| D6
D1 |8 13| D5
D2 |9 12| D4
GND |10 11| D3
+----------+

16450
Asynchronous seria