st16c554 Exar Corporation, st16c554 Datasheet - Page 11

• Manufacturer Part Number: st16c554
• Description: Quad Uart With 16-byte Fifos
• Manufacturer: Exar Corporation

REV. 4.0.1
The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 16 bytes of FIFO which
includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X internal
sampling clock. A bit time is 16X 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 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 16 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.
F
O
2.9
2.9.1
IGURE
UTPUT
MCR Bit-7=1
115.2k
230.4k
19.2k
38.4k
57.6k
1200
2400
4800
9600
100
600
5. B
Data Rate
Transmitter
Transmit Holding Register (THR) - Write Only
AUD
T
ABLE
R
ATE
XTAL1
XTAL2
O
UTPUT
6: T
MCR Bit-7=0
(D
G
153.6k
230.4k
460.8k
921.6k
ENERATOR
EFAULT
19.2k
38.4k
76.8k
YPICAL DATA RATES WITH A
2400
4800
9600
400
Data Rate
Crystal
Buffer
Osc /
)
Clock (Decimal)
D
IVISOR FOR
To Other
Channels
2304
384
192
96
48
24
12
6
4
2
1
16x
14.7456 MH
D
Rate Generator Logic
11
Programmable Baud
IVISOR FOR
Clock (HEX)
2.97V TO 5.5V QUAD UART WITH 16-BYTE FIFO
900
180
C0
0C
60
30
18
06
04
02
01
DLL and DLM
Registers
Z CRYSTAL OR EXTERNAL CLOCK
16x
V
ALUE
P
ROGRAM
DLM
16 X Sampling
09
01
00
00
00
00
00
00
00
00
00
and Receiver
to Transmitter
(HEX)
Rate Clock
V
ALUE
P
ROGRAM
ST16C554/554D
DLL
C0
0C
00
80
60
30
18
06
04
02
01
(HEX)
D
E
ATA
RROR
0
0
0
0
0
0
0
0
0
0
0
R
ATE
(%)