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Tsi572 Hardware Manual
May 18, 2012
Integrated Device Technology
www.idt.com
IDLE_DET Count for Idle Detect Period
The IDLE_DET field is used in two cases. First, it defines the period after reset during which the
I2C_SCLK signal must be seen high in order to call the bus idle. This period is needed to avoid
interfering with an ongoing transaction after reset. Second, it defines the period before a master
transaction during which the I2C_SCLK and I2C_SD signals must both be seen high in order to call the
bus idle.
This period is a protection against external master devices not correctly idling the bus.
•
Period(IDLE_DET) = (IDLE_DET * Period(USDIV)), where USDIV is the microsecond time
defined in the I2C Time Period Divider Register
— Reset time is 51 microseconds
— Tsi572 reset value is 0x0033
A.2.3.4
I2C_SD Setup and Hold Timing Register
The I2C_SD Setup and Hold Timing Register programs the setup and hold times for the I2C_SD signal
when output by either the master or slave interface. It is shadowed during boot loading, and can be
reprogrammed prior to a chain operation without affecting the bus timing for the current EEPROM.
SDA_SETUP Count for the I2C_SD Setup Period
The SDA_SETUP field defines the minimum setup time for the I2C_SD signal; that is, I2C_SD is set
to a desired value prior to rising edge of I2C_SCLK. This applies to both slave and master interface.
•
Period(SDA_SETUP) = (SDA_SETUP * Period(P_CLK)), where P_CLK is 10ns.
— Reset time is 1260 nanoseconds
— Tsi572 reset value is 0x007E
SDA_HOLD Count for I2C_SD Hold Period
The SDA_HOLD field defines the minimum hold time for the I2C_SD signal; that is, I2C_SD valid
past the falling edge of I2C_SCLK. This applies to both slave and master interface.
•
Period(SDA_HOLD) = (SDA_HOLD * Period(P_CLK)), where P_CLK is 10 ns.
— Reset time is 310 nanoseconds
— Tsi572 reset value is 0x001F
A value of zero results in no idle detect period, meaning the bus will be sensed as idle
immediately.
This value should be set to the sum of the I2C_SD setup time and the maximum rise/fall time
of the I2C_SD signal in order to ensure that the signal is valid on the output at the correct
time. This time is different than the raw I2C_SD setup time in the
I
2
C Specification
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