ST16C2550IJ44 Просмотр технического описания (PDF) - Exar Corporation
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ST16C2550IJ44 Datasheet PDF : 39 Pages
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ST16C2550
2.97V TO 5.5V DUART WITH 16-BYTE FIFO
xr
REV. 4.4.0
2.0 FUNCTIONAL DESCRIPTIONS
2.1 CPU Interface
The CPU interface is 8 data bits wide with 3 address lines and control signals to execute data bus read and
write transactions. The C2550 data interface supports the Intel compatible types of CPUs and it is compatible
to the industry standard 16C550 UART. No clock (oscillator nor external clock) is required to operate a data
bus transaction. Each bus cycle is asynchronous using CS#, IOR# and IOW# signals. Both UART channels
share the same data bus for host operations. The data bus interconnections are shown in Figure 3.
FIGURE 3. ST16C2550 DATA BUS INTERCONNECTIONS
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
IOR#
IOW#
UART_CSA#
UART_CSB#
UART_INTA
UART_INTB
TXRDYA#
RXRDYA#
TXRDYB#
RXRDYB#
UART_RESET
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
IOR#
IOW#
UART
Channel A
CSA#
CSB#
INTA
INTB
UART
Channel B
TXRDYA#
RXRDYA#
TXRDYB#
RXRDYB#
VCC
TXA
RXA
DTRA#
RTSA#
CTSA#
DSRA#
CDA#
RIA#
OP2A#
TXB
RXB
DTRB#
RTSB#
CTSB#
DSRB#
CDB#
RIB#
OP2B#
RESET
GND
VCC
Serial Interface of
RS-232, RS-485
Serial Interface of RS-
232, RS-485
2750int
.
2.2 Device Reset
The RESET input resets the internal registers and the serial interface outputs in both channels to their default
state (see Table 11). An active high pulse of at least 40 ns duration will be required to activate the reset
function in the device.
2.3 Channel A and B Selection
The UART provides the user with the capability to bi-directionally transfer information between an external
CPU and an external serial communication device. A logic 0 on chip select pins, CSA# or CSB#, allows the
user to select UART channel A or B to configure, send transmit data and/or unload receive data to/from the
UART. Selecting both UARTs can be useful during power up initialization to write to the same internal registers,
but do not attempt to read from both uarts simultaneously. Individual channel select functions are shown in
Table 1.
TABLE 1: CHANNEL A AND B SELECT
CSA#
CSB#
FUNCTION
1
1
UART de-selected
0
1
Channel A selected
1
0
Channel B selected
0
0
Channel A and B selected
8
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