PIC16F872-I/SP Microchip Technology Inc., PIC16F872-I/SP Datasheet - Page 75

• Manufacturer Part Number: PIC16F872-I/SP
• Description: 28 PIN, 7 KB FLASH, 128 RAM, 22 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F872-I/SP

• A/d Inputs: 5-Channel, 10-Bit
• Cpu Speed: 5 MIPS
• Eeprom Memory: 64 Bytes
• Input Output: 22
• Interface: I2C/SPI
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin SPDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 128 Bytes
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

9.2.18
Multi-Master mode support is achieved by bus arbitra-
tion. When the master outputs address/data bits onto
the SDA pin, arbitration takes place when the master
outputs a '1' on SDA, by letting SDA float high and
another master asserts a '0'. When the SCL pin floats
high, data should be stable. If the expected data on
SDA is a '1' and the data sampled on the SDA pin = '0',
a bus collision has taken place. The master will set the
Bus Collision Interrupt Flag, BCLIF and reset the I
port to its IDLE state. (Figure 9-19).
If a transmit was in progress when the bus collision
occurred, the transmission is halted, the BF flag is
cleared, the SDA and SCL lines are de-asserted, and
the SSPBUF can be written to. When the user services
the bus collision Interrupt Service Routine, and if the
I
asserting a START condition.
FIGURE 9-19:
© 2006 Microchip Technology Inc.
2
C bus is free, the user can resume communication by
SDA
SCL
BCLIF
MULTI -MASTER
COMMUNICATION,
BUS COLLISION, AND
BUS ARBITRATION
BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE
Data changes
while SCL = 0
SDA released
by master
2
C
SDA line pulled low
by another source
If a START, Repeated START, STOP or Acknowledge
condition was in progress when the bus collision
occurred, the condition is aborted, the SDA and SCL
lines are de-asserted, and the respective control bits in
the SSPCON2 register are cleared. When the user ser-
vices the bus collision Interrupt Service Routine, and if
the I
by asserting a START condition.
The master will continue to monitor the SDA and SCL
pins, and if a STOP condition occurs, the SSPIF bit will
be set.
A write to the SSPBUF will start the transmission of
data at the first data bit, regardless of where the trans-
mitter left off when the bus collision occurred.
In Multi-Master mode, the interrupt generation on the
detection of START and STOP conditions allows the
determination of when the bus is free. Control of the I
bus can be taken when the P bit is set in the SSPSTAT
register, or the bus is IDLE and the S and P bits are
cleared.
2
C bus is free, the user can resume communication
Sample SDA. While SCL is high,
data doesn’t match what is driven
by the master.
Bus collision has occurred.
Set bus collision
interrupt
PIC16F872
DS30221C-page 73
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C