ST16C654CJ68 EXAR [Exar Corporation], ST16C654CJ68 Datasheet - Page 19

• Manufacturer Part Number: ST16C654CJ68
• Description: QUAD UART WITH 64-BYTE FIFO AND INFRARED (IrDA) ENCODER/DECODER
• Manufacturer: EXAR [Exar Corporation]

crystal (parallel resonant/ 22-33 pF load) is con-
nected externally between the XTAL1 and XTAL2
pins (see figure ). Alternatively, an external clock
can be connected to the XTAL1 pin to clock the
internal baud rate generator for standard or custom
rates. (see Baud Rate Generator Programming).
The generator divides the input 16X clock by any
divisor from 1 to 2
crystal or external clock by 16. Further division of this
16X clock provides two table rates to support low and
high data rate applications using the same system
design. After a hardware reset and during initializa-
tion, the 654 sets the default baud rate table according
to the state of the CLKSEL. pin. A logic 0 on CLKSEL
will set the 1X clock default whereas, a logic will set the
Baud Rate
Rev. 4.10
BIT-7=1
Output
115.2k
19.2k
38.4k
57.6k
MCR
1200
2400
4800
9600
300
600
50
Table 5, BAUD RATE GENERATOR PROGRAMMING TABLE (7.3728 MHz CLOCK):
Baud Rate
Bit-7=0
Output
153.6k
230.4k
460.8k
16
19.2K
38.4k
76.8k
MCR
1200
2400
4800
9600
200
-1. The 654 divides the basic
16 x Clock
(Decimal)
Divisor
User
2304
384
192
96
48
24
12
6
3
2
1
16 x Clock
Divisor
(HEX)
User
900
180
0C
C0
60
30
18
06
03
02
01
5-83
4X clock default table. Following the default clock rate
selection during initialization, the rate tables can be
changed by the internal register, MCR bit-7. Setting
MCR bit-7 to a logic 1 when CLKSEL is a logic 1
provides an additional divide by 4 whereas, setting
MCR bit-7 to a logic 0 only divides by 1. (See Table 5
and Figure 11). Customized Baud Rates can be
achieved by selecting the proper divisor values for the
MSB and LSB sections of baud rate generator.
Programming the Baud Rate Generator Registers
DLM (MSB) and DLL (LSB) provides a user capability
for selecting the desired final baud rate. The example
in Table 5 below, shows the two selectable baud rate
tables available when using a 7.3728 MHz crystal.
Program
(HEX)
Value
DLM
09
01
00
00
00
00
00
00
00
00
00
ST16C654/654D
Program
(HEX)
Value
DLL
0C
C0
00
80
60
30
18
06
03
02
01