TMP139AIYAHT datasheet(22/58 Pages) TI

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The TMP139 shall NACK the address phase, during a Repeated Start, if there was an error in the previous

transaction.

7.4.5 In Band Interrupt

The In Band Interrupt (IBI) is an elegant method to inform the host of an event in the TMP139. There are two

types of events that the TMP139 generates:

1. Error event: Events corresponding to parity or PEC error.

2. Temperature event: Events corresponding to the temperature exceeding the higher temperature limits or

falling below the lower temperature limits.

By default, all interrupt sources are disabled when the device powers up. The interrupt source can only be

enabled when the device is in I3C basic mode of operation, as enabling the interrupt source shall generate an

IBI which is not allowed in I2C mode of operation. An IBI can only be requested by the TMP139 when the bus

has been in an inactive state for the TAVAL period. Once the condition for an inactive state on the bus is met, and

there is no bus transaction, the TMP139 shall initiate an IBI by driving the SDA low to indicate to the host of a

pending IBI.

7.4.5.1 In Band Interrupt Arbitration Rules

Based on the state of the host controller readiness and due to the fact that there are multiple devices on the bus,

the IBI generation and arbitration must follow some rules, as described below. All of these conditions assume

that the bus has been inactive for TAVAL period.

1. When the host controller starts a write or read with IBI header, TMP139 shall start driving its own address on

the bus. The host on seeing a value other than the IBI header shall no longer drive the SDA, allowing the

TMP139 to transmit its device header along with R/W bit set to 1.

2. If the host controller can accept the IBI from the device, it shall ACK the device address, release the bus on

the falling edge of SCL and shall accept the bytes sent by the TMP139.

3. If the host controller cannot accept the IBI from the device, it shall NACK the device address and issue a Stop

condition on the bus. The TMP139 shall retry another IBI only after TAVAL period.

4. When the host controller starts a write or read without an IBI header to a device on the bus which has a lower

device address than the TMP139, the device on detecting a mismatch, shall no longer participate on the bus

and retry another IBI only after TAVAL period.

5. When the host controller starts a write or read without an IBI header to a device on the bus which has a

higher device address than the TMP139, the device wins the bus arbitration and the host shall no longer

participate on the bus. The host may accept the IBI by sending an ACK or disregard the IBI by sending a

NACK. In the latter case, TMP139 shall retry another IBI only after TAVAL period.

6. When the host controller starts a write or read transaction without an IBI header to the TMP139 which is also

requesting an IBI, either the host or TMP139 can win.

7. If the host controller starts a write transaction, then it shall win the bus arbitration and the TMP139 shall let go

of the bus. The TMP139 shall retry another IBI only after TAVAL period.

8. If the host controller starts a read transaction, then all the bits shall match. However at this point the host is

expecting an ACK from the TMP139 for the read request, while the TMP139 is waiting for an ACK from the

host for the IBI. As a result there shall be a NACK on the bus. In such a case, the TMP139 shall retry the IBI

only after TAVAL period. However if the host issues start (or Repeated Start) and attempts the read transaction

before the TAVAL period, it shall get an ACK from the TMP139 and the host read shall win the arbitration on

the bus.

9. As described above, in the case when there are multiple devices initiating an IBI at the same time, the device

which has the lowest device address shall win the bus arbitration and the TMP139 when it detects a loss on

the bus arbitration, shall retry another IBI only after TAVAL period

7.4.5.2 In Band Interrupt Bus Transaction

As shown in Figure 7-23 and Figure 7-24, when the device has to send an IBI, wins arbitration on the bus and

the IBI is ACK by the host, it shall always send the mandatory data byte (MDB) as 8'h00, followed by the MR51

and MR52 register values. After transmitting the last byte, it shall set the T-bit as 0, after which the host controller

must send a Stop condition on the bus.

TMP139

SNIS217 – DECEMBER 2020

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