ST16C450 Exar Corporation, ST16C450 Datasheet - Page 12

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

ST16C450
REGISTER FUNCTIONAL DESCRIPTIONS
The following table delineates the assigned bit functions for the twelve ST16C450 internal registers. The as-
signed bit functions are more fully defined in the following paragraphs.
Note *3: The Special register set is accessible only when LCR bit-7 is set to a logic 1.
Note *5: The value represents the register’s initialized HEX value. An “X” signifies a 4-bit un-initialized nibble.
Rev. 4.20
A2 A1 A0
0
0
0
0
0
0
1
1
1
1
0
Table 4, ST16C450 INTERNAL REGISTERS
General Register Set
Special Register Set: Note *3
0
0
0
1
1
0
0
1
1
0
0
0
0
1
0
1
0
1
0
1
0
1
RHR [XX]
MSR [X0]
THR [XX]
MCR [00]
SPR [FF]
DLM [XX]
Register
[Default]
LCR [00]
DLL [XX]
LSR [60]
IER [00]
ISR [01]
Note *5
divisor
enable
BIT-7
bit-15
latch
bit-7
bit-7
bit-7
bit-7
CD
0
0
0
0
empty
BIT-6
trans.
bit-14
break
bit-6
bit-6
bit-6
bit-6
set
RI
0
0
0
holding
empty
BIT-5
trans.
bit-13
parity
DSR
bit-5
bit-5
bit-5
bit-5
set
0
0
0
12
interrupt
bit-12
BIT-4
break
parity
even
back
CTS
bit-4
bit-4
loop
bit-4
bit-4
0
0
interrupt
framing
modem
priority
enable
status
bit-11
BIT-3
parity
-OP2
error
delta
bit-3
bit-3
bit-2
bit-3
bit-3
-CD
INT
interrupt
receive
priority
status
bit-10
BIT-2
-OP1
parity
error
delta
bit-2
bit-2
bit-1
bit-2
bit-2
stop
INT
line
bits
-RI
transmit
register
overrun
holding
priority
length
BIT-1
-RTS
-DSR
word
error
delta
bit-9
bit-1
bit-1
bit-0
bit-1
bit-1
bit-1
INT
register
receive
holding
receive
length
BIT-0
status
-DTR
ready
-CTS
word
delta
bit-8
bit-0
bit-0
bit-0
bit-0
bit-0
data
INT