ST16C450
SYMBOL DESCRIPTION
Symbol
Pin
44
Signal
type
Pin Description
40
48
A0
28
31
30
29
25
28
I
I
I
I
Address-0 Select Bit Internal registers address selection.
Address-1 Select Bit Internal registers address selection.
Address-2 Select Bit Internal registers address selection.
A1
27
26
22
27
26
20
A2
IOR
Read data strobe. Its function is the same as -IOR (see -
IOR), except it is active high. Either an active -IOR or IOR
is required to transfer data from 16C450 to CPU during a
read operation.
CS0
CS1
-CS2
IOW
12
13
14
19
14
15
16
21
9
I
I
I
I
Chip Select-0. Logical 1 on this pin provides the chip select-
0 function.
10
11
17
Chip Select-1. Logical 1 on this pin provides the chip select-
1 function.
Chip Select -2. Logical 0 on this pin provides the chip select-
2 function.
Write data strobe. Its function is the same as -IOW (see -
IOW), but it acts as an active high input signal. Either -IOW
or IOW is required to transfer data from the CPU to
ST16C450 during a write operation.
-AS
25
28
24
I
Address Strobe. A logic 0 transition on -AS latches the state
of the chip selects and the register select bits, A0-A2. This
input is used when address and chip selects are not stable
for the duration of a read or write operation, i.e., a micropro-
cessor that needs to de-multiplex the address and data bits.
If not required, the -AS input can be permanently tied to a
logic 0 (it is edge triggered).
D0-D7
GND
1-8
20
2-9
22
43-47
2-4
I/O
Data Bus (Bi-directional) - These pins are the eight bit, tri-
state data bus for transferring information to or from the
controlling CPU. D0 is the least significant bit and the first
data bit in a transmit or receive serial data stream.
18
Pwr
SignalandPowerGround.
Rev.4.20
4
EXAR [ EXAR CORPORATION ]
