21 I2C Slave (I2CS)
S1C17602 TECHNICAL MANUAL
EPSON
21-5
I2CS
Asynchronous address detection
The I2C slave module operation clock (PCLK) frequency must be set eight-times or higher than the transfer rate
during data transfer. However, the PCLK frequency can be lowered to reduce current consumption if no other
processing is required during standby for data transfer. The asynchronous address detection function is provided
to detect the I2C slave address sent from the master in this status.
The asynchronous address detection function in this module is disabled by default. When using the
asynchronous address detection function, set ASDET_EN (D1/I2CS_CTL register) to 1.
ASDET_EN: Async. Address Detection On/Off Bit in the I2C Slave Control (I2CS_CTL) Register (D1/0x4366)
If the slave address sent from the master has matched with one that has been set in this I2C slave module when
the asynchronous address detection function has been enabled, the I2C slave module generates a bus status
interrupt and returns NAK to the I2C master to request for resending the slave address. Set the PCLK frequency
to eight-times or higher than the transfer rate and reset ASDET_EN to 0 in the interrupt handler routine. Data
transfer will be able to resume normally after the master retries transmission. After the master generates a
STOP condition to put the I2C bus into free status, the asynchronous address detection function can be enabled
again to lower the operating speed.
Notes: When the asynchronous address detection function is enabled, the I2C signals are input
without passing through the noise filter. Therefore, the slave address may not be detected in a
high-noise environment.
When the asynchronous address detection function is enabled, data transfer cannot be
performed even if the PCLK frequency is eight-times or higher than the transfer rate. Be sure
to disable the asynchronous address detection function during normal operation.
Noise filter
The I2C slave module contains a function to remove noise from the SDA1 and SCL1 input signals. This
function is enabled by setting NF_EN (D2/I2CS_CTL register) to 1.
NF_EN: Noise Filter On/Off Bit in the I2C Slave Control (I2CS_CTL) Register (D2/0x4366)