Z8 Encore!® Motor Control Flash MCUs
Product Specification
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The I2CSLVAD Register is added to provide programming capabilities for the slave
address.
The ACKV bit in the I2CSTATE Register enables the master to check the Acknowl-
edge from the slave before sending the next byte.
Support for multimaster environments—if arbitration is lost when operating as a mas-
ter, the ARBLST bit in the I2CISTAT Register is set and the mode automatically
switches to SLAVE mode.
Operation
The I2C Master/Slave Controller operates in MASTER/SLAVE mode, SLAVE ONLY
mode, or with master arbitration. In MASTER/SLAVE mode, it can be used as the only
master on the bus or as one of several masters on the bus, with arbitration. In a multimaster
environment, the controller switches from MASTER to SLAVE mode upon losing arbitra-
tion.
Though slave operation is fully supported in MASTER/SLAVE mode, if a device is
intended to operate only as a slave, then SLAVE ONLY mode can be selected. In SLAVE
ONLY mode, the device will not initiate a transaction, even if the software inadvertently
sets the START bit.
SDA and SCL Signals
The I2C circuit sends all addresses, data, and Acknowledge signals over the SDA line,
most-significant bit first. SCL is the clock for the I2C bus. When the SDA and SCL pin
alternate functions are selected for their respective GPIO ports, the pins are automatically
configured for open-drain operation.
The master is responsible for driving the SCL clock signal. During the Low period of the
clock, a slave can hold the SCL signal Low to suspend the transaction if it is not ready to
proceed. The master releases the clock at the end of the Low period and notices that the
clock remains Low instead of returning to a High level. When the slave releases the clock,
the I2C master continues the transaction. All data is transferred in bytes; there is no limit to
the amount of data transferred in one operation. When transmitting address, data, or an
Acknowledge, the SDA signal changes in the middle of the Low period of SCL. When
receiving address, Data or an Acknowledge, the SDA signal is sampled in the middle of
the High period of SCL.
A low-pass digital filter can be applied to the SDA and SCL receive signals by setting the
Filter Enable (FILTEN) bit in the I2C Control Register. When the filter is enabled, any
glitch that is less than a system clock period in width will be rejected. This filter should be
enabled when running in I2C FAST mode (400kbps), and can also be used at lower data
rates.
I2C Master/Slave Controller
P R E L I M I N A R Y
PS024604-1005
ZILOG [ ZILOG, INC. ]
