XR16C854CV EXAR [Exar Corporation], XR16C854CV Datasheet - Page 14

• Manufacturer Part Number: XR16C854CV
• Description: 2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

XR16C854/854D
2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 128 bytes of FIFO which
includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X internal
clock. A bit time is 16 clock periods. The transmitter sends the start-bit followed by the number of data bits,
inserts the proper parity-bit if enabled, and adds the stop-bit(s). The status of the TX FIFO and TSR are
reported in the Line Status Register (LSR bit-5 and bit-6).
The transmit holding register is an 8-bit register providing a data interface to the host processor. The host
writes transmit data byte to the THR to be converted into a serial data stream including start-bit, data bits,
parity-bit and stop-bit(s). The least-significant-bit (Bit-0) becomes first data bit to go out. The THR is the input
register to the transmit FIFO of 128 bytes when FIFO operation is enabled by FCR bit-0. Every time a write
operation is made to the THR, the FIFO data pointer is automatically bumped to the next sequential data
location.
The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the
data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled
by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty.
O
2.11
2.11.1
2.11.2
UTPUT
MCR Bit-7=1
230.4k
115.2k
19.2k
38.4k
57.6k
1200
2400
4800
9600
100
600
Data Rate
Transmitter
Transmit Holding Register (THR) - Write Only
Transmitter Operation in non-FIFO Mode
F
T
IGURE
ABLE
XTAL1
XTAL2
O
UTPUT
6. B
6: T
MCR Bit-7=0
(D
153.6k
230.4k
460.8k
921.6k
EFAULT
19.2k
38.4k
76.8k
YPICAL DATA RATES WITH A
2400
4800
9600
AUD
400
Data Rate
R
Crystal
Buffer
)
Osc/
ATE
G
Clock (Decimal)
D
ENERATOR AND
IVISOR FOR
2304
384
192
96
48
24
12
6
4
2
1
Divide by 4
Divide by 1
Prescaler
Prescaler
16x
14.7456 MH
P
D
14
RESCALER
IVISOR FOR
Clock (HEX)
MCR Bit-7=0
MCR Bit-7=1
(default)
900
180
C0
0C
60
30
18
06
04
02
01
Z CRYSTAL OR EXTERNAL CLOCK
16x
Baud Rate
DLL and DLM
Generator
Registers
Logic
V
ALUE
P
ROGRAM
DLM
09
01
00
00
00
00
00
00
00
00
00
(HEX)
Rate Clock to
Transmitter
Sampling
V
16X
ALUE
P
ROGRAM
DLL
C0
0C
00
80
60
30
18
06
04
02
01
(HEX)
xr
D
E
REV. 3.0.1
ATA
RROR
0
0
0
0
0
0
0
0
0
0
0
R
ATE
(%)