ADUC834 Analog Devices, ADUC834 Datasheet - Page 57

• Manufacturer Part Number: ADUC834
• Description: Precision Analog Microcontroller: 1MIPS 8052 MCU + 62kB Flash + 16/24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC834

• Mcu Core: 8052
• Mcu Speed (mips): 1
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 4
• Other: PWM

UART SERIAL INTERFACE
The serial port is full duplex, meaning it can transmit and
receive simultaneously. It is also receive-buffered, meaning it
can commence reception of a second byte before a previously
received byte has been read from the receive register. However,
if the first byte still has not been read by the time reception of
the second byte is complete, the first byte will be lost. The
physical interface to the serial data network is via Pins
SCON
SFR Address
Power-On Default Value
Bit Addressable
Bit
7
6
5
4
3
2
1
0
UART OPERATING MODES
Mode 0: 8-Bit Shift Register Mode
Mode 0 is selected by clearing both the SM0 and SM1 bits in the
SFR SCON. Serial data enters and exits through RxD. TxD outputs
the shift clock. Eight data bits are transmitted or received. Trans-
mission is initiated by any instruction that writes to SBUF. The
data is shifted out of the RxD line. The 8 bits are transmitted
with the least-significant bit (LSB) first, as shown in Figure 54.
Reception is initiated when the Receive Enable bit (REN) is
1 and the Receive Interrupt bit (RI) is 0. When RI is cleared,
the data is clocked into the RxD line and the clock pulses are
output from the TxD line.
REV. A
Name
SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Description
UART Serial Mode Select Bits.
These bits select the Serial Port operating mode as follows:
SM0
0
0
1
1
Multiprocessor Communication Enable Bit.
Enables multiprocessor communication in Modes 2 and 3. In Mode 0, SM2 should be cleared. In
Mode 1, if SM2 is set, RI will not be activated if a valid stop bit was not received. If SM2 is cleared,
RI will be set as soon as the byte of data has been received. In Modes 2 or 3, if SM2 is set, RI will not be
activated if the received ninth data bit in RB8 is 0. If SM2 is cleared, RI will be set as soon as the byte
of data has been received.
Serial Port Receive Enable Bit.
Set by user software to enable serial port reception.
Cleared by user software to disable serial port reception.
Serial Port Transmit (Bit 9).
The data loaded into TB8 will be the ninth data bit that will be transmitted in Modes 2 and 3.
Serial Port Receiver Bit 9.
The ninth data bit received in Modes 2 and 3 is latched into RB8. For Mode 1, the stop bit is latched into RB8.
Serial Port Transmit Interrupt Flag.
Set by hardware at the end of the eighth bit in Mode 0, or at the beginning of the stop bit in
Modes 1, 2, and 3.
TI must be cleared by user software.
Serial Port Receive Interrupt Flag.
Set by hardware at the end of the eighth bit in Mode 0, or halfway through the stop bit in
Modes 1, 2, and 3.
RI must be cleared by software.
UART Serial Port Control Registers
SM1
0
1
0
1
98H
00H
Yes
Table XXX. SCON SFR Bit Designations
Selected Operating Mode
Mode 0: Shift Register, fixed baud rate (f
Mode 1: 8-bit UART, variable baud rate
Mode 2: 9-bit UART, fixed baud rate (f
Mode 3: 9-bit UART, variable baud rate
–57–
(SHIFT CLOCK)
RxD(P3.0) and TxD(P3.1), while the SFR interface to the UART
comprises the following registers:
SBUF
The serial port receive and transmit registers are both accessed
through the SBUF SFR (SFR address = 99H). Writing to SBUF
loads the transmit register and reading SBUF accesses a physically
separate receive register.
(DATA OUT)
Figure 54. UART Serial Port Transmission, Mode 0
CORE
CLK
ALE
RxD
TxD
S1
S2
CORE
MACHINE
DATA BIT 0
CYCLE 1
CORE
S3
S4
/64) or (f
/12)
S5
S6
S1
DATA BIT 1
CORE
S2
MACHINE
CYCLE 2
S3
/32)
S4
MACHINE
CYCLE 7
DATA BIT 6
S4
S5
ADuC834
S6
S1
S2
MACHINE
DATA BIT 7
CYCLE 8
S3
S4
S5
S6