ADUC824 Analog Devices, ADUC824 Datasheet - Page 59

• Manufacturer Part Number: ADUC824
• Description: Precision Analog Microcontroller: 1MIPS 8052 MCU + 8kB Flash + 16/24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC824

• Mcu Core: 8052
• Mcu Speed (mips): 1
• Sram (bytes): 256Bytes
• Gpio Pins: 34
• Adc # Channels: 4

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:
Modes 1 and 3 Baud Rate = (2
The Timer 1 interrupt should be disabled in this application. The
Timer itself can be configured for either timer or counter opera-
tion, 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 = 0100Binary). In that case, the baud
rate is given by the formula:
Modes 1 and 3 Baud Rate =
A very low baud rate can also be achieved with Timer 1 by leaving
the Timer 1 interrupt enabled, and configuring the timer to run
as a 16-bit timer (high nibble of TMOD = 0100Binary), and using
the Timer 1 interrupt to do a 16-bit software reload. Table XXVIII
below, shows some commonly-used baud rates and how they
might be calculated from a core clock frequency of 1.5728 MHz
and 12.58 MHz. Generally speaking, a 5% error is tolerable
using asynchronous (start/stop) communications.
Ideal
Baud
9600
2400
1200
1200
(2
SMOD
Table XXVIII. Commonly Used Baud Rates, Timer 1
/32) × (Core Clock/(12 × [256-TH1]))
Core
CLK
12.58
12.58
12.58
1.57
NOTE: OSC. FREQ. IS DIVIDED BY 2, NOT 12.
NOTE AVAILABILITY OF ADDITIONAL
EXTERNAL INTERRUPT
THE CORE CLOCK IS THE OUTPUT OF THE PLL AS DESCRIBED ON PAGE 42.
TRANSITION
SMOD
Value
1
1
1
1
T2EX
DETECTOR
PIN
PIN
CORE
CLK
T2
TH1-Reload
Value
–7 (F9h)
–27 (E5h)
–55 (C9h)
–7 (F9h)
SMOD
2
/32) × (Timer 1 Overflow Rate)
C/T2 = 0
C/T2 = 1
EXEN2
CONTROL
CONTROL
Actual
9362
2427
1192
1170
Baud
TR2
EXF
2
%
Error
2.5
1.1
0.7
2.5
RCAP2L
(8-BITS)
TL2
TIMER 2
INTERRUPT
RCAP2H
(8-BITS)
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.
Modes 1 and 3 Baud Rate = (1/16) × (Timer 2 Overflow Rate)
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. Hence, it increments six times faster than Timer 1, and
therefore 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 42.
In this case, the baud rate is given by the formula:
Modes 1 and 3 Baud Rate
Table XXIX shows some commonly used baud rates and how they
might be calculated from a core clock frequency of 1.5728 MHz
and 12.5829 MHz.
Ideal
Baud
19200
9600
2400
1200
9600
2400
1200
TH2
= (Core Clk)/(32 × [65536 – (RCAP2H, RCAP2L)])
Table XXIX. Commonly Used Baud Rates, Timer 2
RELOAD
OVERFLOW
Core
CLK
12.58
12.58
12.58
12.58
1.57
1.57
1.57
TIMER 2
RCAP2H
Value
–1 (FFh)
–1 (FFh)
–1 (FFh)
–2 (FEh)
–1 (FFh)
–1 (FFh)
–1 (FFh)
1
1
OVERFLOW
2
0
TIMER 1
0
0
1
RCAP2L
Value
–20 (ECh)
–41 (D7h)
–164 (5Ch) 2398
–72 (B8h)
–5 (FBh)
–20 (ECh)
–41 (D7h)
TCLK
RCLK
16
16
SMOD
RX
CLOCK
TX
CLOCK
ADuC824
Actual
19661
9591
1199
9830
2458
1199
Baud
%
Error
2.4
0.1
0.1
0.1
2.4
2.4
0.1