EVAL-ADUC812QS Analog Devices Inc, EVAL-ADUC812QS Datasheet - Page 37

• Manufacturer Part Number: EVAL-ADUC812QS
• Description: KIT DEV FOR ADUC812 QUICK START
• Manufacturer: Analog Devices Inc
• Series: QuickStart™ Kitr
• Type: MCUr

Specifications of EVAL-ADUC812QS

• Rohs Status: RoHS non-compliant
• Contents: Evaluation Board, Power Supply, Cable, Software and Documentation
• For Use With/related Products: ADuC812

Timer 1 Generated Baud Rates
When Timer 1 is used as the baud rate generator, the baud rates
in Modes 1 and 3 are determined by the Timer 1 overflow rate and
the value of SMOD as follows:
The Timer 1 interrupt should be disabled in this application.
The timer itself can be configured for either timer or counter
operation, and in any of its three running modes. In the most
typical application, it is configured for timer operation in the
Autoreload mode (high nibble of TMOD = 0010 binary). In that
case, the baud rate is given by the formula:
Table XX shows some commonly used baud rates and how they
might be calculated from a core clock frequency of 11.0592 MHz
and 12 MHz. Generally speaking, a 5% error is tolerable using
asynchronous (start/stop) communications.
Ideal
Baud
9600
19200
9600
2400
Timer 2 Generated Baud Rates
Baud rates can also be generated using Timer 2. Using Timer 2 is
similar to using Timer 1 in that the timer must overflow 16 times
before a bit is transmitted/received. Because Timer 2 has a 16-bit
Autoreload mode, a wider range of baud rates is possible using
Timer 2.
REV. E
Table XX. Commonly Used Baud Rates, Timer 1
(
Modes and Baud Rate
Core
CLK
12
11.0592
11.0592
11.0592
2
SMOD
(
Modes and Baud Rate
2
1
SMOD
32
TRANSITION
NOTE: AVAILABILITY OF ADDITIONAL
EXTERNAL INTERRUPT
T2EX
DETECTOR
NOTE: OSCILLATOR FREQUENCY
IS DIVIDED BY 2, NOT 12.
)
CORE
PIN
PIN
CLK
T2
1
1
0
0
×
SMOD
Value
1
3
32
(
Core Clock
)
×
3
(
Timer Overflow Rate
2
TH1-Reload
Value
–7 (F9H)
–3 (FDH)
–3 (FDH)
–12 (F4H)
=
(
1
12
C/T2 = 0
C/T2 = 1
×
=
EXEN2
[
256
CONTROL
CONTROL
−
Figure 34. Timer 2, UART Baud Rates
TR2
TH
Actual
Baud
8929
19200
9600
2400
)
1
]
)
EXF
)
2
%
7
0
Error
0
0
RCAP2L
(8 BITS)
TL2
TIMER 2
INTERRUPT
–37–
RCAP2H
(8 BITS)
Therefore, when Timer 2 is used to generate baud rates, the
timer increments every two clock cycles and not every core
machine cycle as before. Therefore, it increments six times
faster than Timer 1, and baud rates six times faster are possible.
Because Timer 2 has 16-bit autoreload capability, very low baud
rates are still possible.
Timer 2 is selected as the baud rate generator by setting the TCLK
and/or RCLK in T2CON. The baud rates for transmit and receive
can be simultaneously different. Setting RCLK and/or TCLK puts
Timer 2 into its baud rate generator mode as shown in Figure 34.
In this case, the baud rate is given by the formula:
Table XXI shows some commonly used baud rates and how they
might be calculated from a core clock frequency of 11.0592 MHz
and 12 MHz.
Ideal
Baud
19200
9600
2400
1200
19200
9600
2400
1200
TH2
(
Modes and Baud Rate
Core Clk
Table XXI. Commonly Used Baud Rates, Timer 2
RELOAD
OVERFLOW
Core
CLK
12
12
12
12
11.0592
11.0592
11.0592
11.0592
TIMER 2
1
)
(
Modes and Baud Rate
(
1 16
32
3
×
1
1
)
RCAP2H
Value
–1 (FFH)
–1 (FFH)
–1 (FFH)
–2 (FEH)
–1 (FFH)
–1 (FFH)
–1 (FFH)
–2 (FFH)
[
×
1
OVERFLOW
65536
2
(
TIMER 1
0
Timer Overflow Rate
0
0
3
1
−
2
=
TCLK
RCLK
(
RCAP H RCAP L
16
16
RCAP2L
Value
–20 (ECH) 19661
–41 (D7H) 9591
–164 (5CH) 2398
–72 (B8H)
–18 (EEH) 19200
–36 (DCH) 9600
–144 (70H) 2400
–32 (E0H)
SMOD
2
RX
CLOCK
TX
CLOCK
=
,
ADuC812
)
Actual
Baud
1199
1200
2
)
]
)
%
Error
2.4
0.1
0.1
0.1
0
0
0
0