C8051F236 Silicon Laboratories Inc, C8051F236 Datasheet - Page 122

• Manufacturer Part Number: C8051F236
• Description: IC 8051 MCU 8K FLASH 48TQFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F2xxr

Specifications of C8051F236

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, WDT
• Number Of I /o: 32
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 48-TQFP, 48-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

C8051F2xx
16.2. Multiprocessor Communications
Modes 2 and 3 support multiprocessor communication between a master processor and one or more slave
processors by special use of the ninth data bit. When a master processor wants to transmit to one or more
slaves, it first sends an address byte to select the target(s). An address byte differs from a data byte in that
its ninth bit is logic 1; in a data byte, the ninth bit is always set to logic 0.
Setting the SM2 bit (SCON.5) of a slave processor configures its UART such that when a stop bit is
received, the UART will generate an interrupt only if the ninth bit is logic one (RB8 = 1) signifying an
address byte has been received. In the UART's interrupt handler, software will compare the received
address with the slave's own assigned 8-bit address. If the addresses match, the slave will clear its SM2 bit
to enable interrupts on the reception of the following data byte(s). Slaves that weren't addressed leave
their SM2 bits set and do not generate interrupts on the reception of the following data bytes, thereby
ignoring the data. Once the entire message is received, the addressed slave resets its SM2 bit to ignore
all transmissions until it receives the next address byte.
Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple
slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master
processor can be configured to receive all transmissions or a protocol can be implemented such that the
master/slave role is temporarily reversed to enable half-duplex transmission between the original master
and slave(s).
122
Oscillator Frequency
16.5888
14.7456
12.9024
22.1184
11.0592
23.592
18.432
(MHz)
9.216
Figure 16.7. UART Multi-Processor Mode Interconnect Diagram
24.0
RX
Master
Device
Table 16.2. Oscillator Frequencies for Standard Baud Rates
TX
RX
Device
Slave
Divide Factor
TX
208
205
192
160
144
128
112
96
80
RX
Rev. 1.6
Device
Slave
Timer 1 Load Value*
TX
0xFA
0xFB
0xF3
0xF3
0xF4
0xF6
0xF7
0xF8
0xF9
RX
Device
Slave
TX
Resulting Baud Rate**
115200 (115384)
115200 (113423)
VDD
115200
115200
115200
115200
115200
115200
115200