mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 185

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

MC68HC908BD48
Freescale Semiconductor
—
Rev. 2.1
MMAST — Master Control Bit
MMRW — Master Read/Write
MMBR2–MMBR0 — Baud Rate Select
This bit is set to initiate a master mode transfer. In master mode, the
module generates a start condition to the SDA and SCL lines,
followed by sending the calling address stored in MMADR.
When the MMAST bit is cleared by MMNAKIF set (no acknowledge)
or by software, the module generates the stop condition to the lines
after the current byte is transmitted.
If an arbitration loss occurs (MMALIF = 1), the module reverts to slave
mode by clearing MMAST, and releasing SDA and SCL lines
immediately.
This bit is cleared by writing "0" to it or by reset.
This bit will be transmitted out as bit 0 of the calling address when the
module sets the MMAST bit to enter master mode. The MMRW bit
determines the transfer direction of the data bytes that follows. When
it is "1", the module is in master receive mode. When it is "0", the
module is in master transmit mode. Reset clears this bit.
These three bits select one of eight clock rates as the master clock
when the module is in master mode.
Since this master clock is derived the CPU bus clock, the user
program should not execute the WAIT instruction when the MMIIC
module in master mode. This will cause the SDA and SCL lines to
hang, as the WAIT instruction places the MCU in WAIT mode, with
CPU clock is halted. These bits are cleared upon reset. (See
14-3 . Baud Rate
1 = Master mode operation
0 = Slave mode operation
1 = Master mode receive
0 = Master mode transmit
Multi-Master IIC Interface (MMIIC)
Select.)
Multi-Master IIC Interface (MMIIC)
Data Sheet
Table
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