EVAL-ADUC842QSZ Analog Devices Inc, EVAL-ADUC842QSZ Datasheet - Page 67

• Manufacturer Part Number: EVAL-ADUC842QSZ
• Description: Analog MCU Evaluation Board
• Manufacturer: Analog Devices Inc
• Series: QuickStart™ Kitr
• Type: MCUr

Specifications of EVAL-ADUC842QSZ

• Silicon Manufacturer: Analog Devices
• Core Architecture: 8052
• Silicon Core Number: ADuC842
• Tool / Board Applications: General Purpose MCU, MPU, DSP, DSC
• Mcu Supported Families: ADUC8xx
• Contents: Evaluation Board, Power Supply, Cable, Software and Documentation
• Development Tool Type: Hardware - Eval/Demo Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: ADuC824
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Mode 3: 9-Bit UART with Variable Baud Rate
Mode 3 is selected by setting both SM0 and SM1. In this mode,
the 8051 UART serial port operates in 9-bit mode with a vari-
able baud rate determined by either Timer 1 or Timer 2. The
operation of the 9-bit UART is the same as for Mode 2, but the
baud rate can be varied as for Mode 1.
In all four modes, transmission is initiated by any instruction
that uses SBUF as a destination register. Reception is initiated in
Mode 0 by the condition RI = 0 and REN = 1. Reception is
initiated in the other modes by the incoming start bit if REN = 1.
UART Serial Port Baud Rate Generation
Mode 0 Baud Rate Generation
The baud rate in Mode 0 is fixed.
Mode 2 Baud Rate Generation
The baud rate in Mode 2 depends on the value of the SMOD bit
in the PCON SFR. If SMOD = 0, the baud rate is 1/32 of the
core clock. If SMOD = 1, the baud rate is 1/16 of the core clock:
Modes 1 and 3 Baud Rate Generation
The baud rates in Modes 1 and 3 are determined by the over-
flow rate in Timer 1 or Timer 2, or in both (one for transmit
and the other for receive).
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
Mode 0 Baud Rate = (Core Clock Frequency/12)
Mode 2 Baud Rate = (2
NOTE: AVAILABILITY OF ADDITIONAL
EXTERNAL INTERRUPT
TRANSITION
T2EX
*CORE CLK IS DEFINED BY THE CD BITS IN PLLCON
DETECTOR
PIN
PIN
CORE
CLK*
T2
SMOD
SMOD
/32 × [Core Clock Frequency])
/32 × (Timer 1 Overflow Rate)
C/ T2 = 0
C/ T2 = 1
EXEN2
CONTROL
CONTROL
TR2
Figure 73. Timer 2, UART Baud Rates
EXF 2
Rev. 0 | Page 67 of 88
RCAP2L
(8 BITS)
TL2
TIMER 2
INTERRUPT
RCAP2H
(8 BITS)
TH2
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
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.
Therefore, when Timer 2 is used to generate baud rates, the
timer increments every two clock cycles rather than every core
machine cycle as before. Thus, it increments six times faster
than Timer 1, and therefore baud rates six times faster are possi-
ble. 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 73.
In this case, the baud rate is given by the formula
RELOAD
OVERFLOW
Modes 1 and 3 Baud Rate =
(2
Modes 1 and 2 Baud Rate = (1/16) × (Timer 2 Overflow Rate)
Modes 1 and 3 Baud Rate =
(Core Clock)/(16 × [65536 − (RCAP 2H, RCAP 2L)])
TIMER 2
SMOD
/32) × (Core Clock/ [256 − TH1])
1
1
OVERFLOW
2
TIMER 1
0
0
0
ADuC841/ADuC842/ADuC843
1
RCLK
TCLK
16
16
SMOD
RX
CLOCK
TX
CLOCK