ST16C450 Exar Corporation, ST16C450 Datasheet - Page 4

• Manufacturer Part Number: ST16C450
• Description: UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER (UART)
• Manufacturer: Exar Corporation

ST16C450
SYMBOL DESCRIPTION
A0
A1
A2
IOR
CS0
CS1
IOW
-AS
D0-D7
GND
-CS2
Symbol
Rev. 4.20
1-8
40
27
26
22
12
13
14
19
25
28
20
Pin
2-9
44
31
30
29
25
14
15
16
21
28
22
43-47
2-4
48
28
27
26
20
10
11
17
24
18
9
Signal
type
Pwr
I/O
I
I
I
I
I
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.
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.
Chip Select-0. Logical 1 on this pin provides the chip select-
0 function.
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.
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).
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.
Signal and Power Ground.
4
Pin Description