aduc7062 Analog Devices, Inc., aduc7062 Datasheet - Page 74

• Manufacturer Part Number: aduc7062
• Description: Low-power, Precision Analog Microcontroller, Dual ?-? Adcs, Flash/ee, Arm7tdmi
• Manufacturer: Analog Devices, Inc.

ADuC7060/ADuC7061/ADuC7062
UART SERIAL INTERFACE
The ADuC7060 features a 16450-compatible UART. The UART
is a full-duplex, universal, asynchronous receiver/transmitter.
A UART performs serial-to-parallel conversion on data charac-
ters received from a peripheral device, and parallel-to-serial
conversion on data characters received from the ARM7TDMI.
The UART features a fractional divider that facilitates high
accuracy baud rate generation and a network addressable mode.
The UART functionality is available on the P1.0/RxD and
P1.1/TxD pins of the ADuC7060.
The serial communication adopts an asynchronous protocol
that supports various word length, stop bits, and parity genera-
tion options selectable in the configuration register.
BAUD RATE GENERATION
The ADuC7060 features two methods of generating the UART
baud rate: normal 450 UART baud rate generation and
ADuC7060 fractional divider.
Normal 450 UART Baud Rate Generation
The baud rate is a divided version of the core clock using the
value in COMDIV0 and COMDIV1 MMRs (16-bit value, DL).
The standard baud rate generator formula is
Table 82 lists common baud rate values.
Table 82. Baud Rate Using the Standard Baud Rate Generator
Baud Rate
9600
19,200
115,200
9600
19,200
ADuC706x Fractional Divider
The fractional divider combined with the normal baud rate
generator allows the generation of accurate, high speed baud rates.
Baud
CLOCK
CORE
Figure 22. Fractional Divider Baud Rate Generation
rate
CD
0
0
0
3
3
=
/(M + N/2048)
10
16
.
×
24
/2
2
DL
0x21
0x11
0x3
0x4
0x2
MHz
×
DL
FBEN
Actual Baud Rate
9696
18,824
106,667
10,000
20,000
/16DL
UART
% Error
1.01%
1.96%
7.41%
4.17%
4.17%
Rev. PrA | Page 74 of 100
(1)
Calculation of the baud rate using a fractional divider is as
follows:
Table 83 lists common baud rate values.
Table 83. Baud Rate Using the Fractional Baud Rate Generator
Baud
Rate
9600
19,200
115,200
UART REGISTER DEFINITION
The UART interface consists of the following nine registers:
COMTX: 8-bit transmit register
COMRX: 8-bit receive register
COMDIV0: divisor latch (low byte)
COMDIV1: divisor latch (high byte)
COMCON0: line control register
COMSTA0: line status register
COMIEN0: interrupt enable register
COMIID0: interrupt identification register
COMDIV2: 16-bit fractional baud divide register
COMTX, COMRX, and COMDIV0 share the same address
location. COMTX and COMRX can be accessed when Bit 7 in
the COMCON0 register is cleared. COMDIV0 can be accessed
when Bit 7 of COMCON0 is set.
Baud
M
+
2048
rate
N
CD
0
0
0
=
=
16
DL
0x21
0x10
0x2
Baud
Preliminary Technical Data
×
DL
10
rate
10
×
M
1
1
1
.
.
24
2
24
×
×
MHz
MHz
16
(
N
21
85
796
M
×
+
DL
2048
Actual
Baud Rate
9598.55
19,203
115,218
N
×
2
)
% Error
0.015%
0.015%
0.015%
(2)