Rainbow Electronics LM95010 - Manual (Page 10)

1.0 Functional Description
(Continued)
1.3.2 Read Transaction
During a read transaction, the master reads data from a
register at a specified address within a slave. A read trans-
action begins with a Start Bit and ends with an ACK bit, as
shown in Figure 7.
• Device Number This is the address of the LM95010
device accessed. Address "000" is a broadcast address
and can be responded to by all the slave devices. The
LM95010 ignores the broadcast address during a read
transaction.
• Internal Address The address of a register within the
LM95010 that is read.
• Read/Write (R/W) A "1" indicates a read transaction.
• Data Bits During a read transaction the data bits are
driven by the LM95010. Data is transferred serially with
the most significant bit first. This allows throughput opti-
mization based on the information that needs to be read.
The LM95010 supports 8-bit or 16-bit data fields, as
described in Section 2.0 "Register Set".
• Even Parity (EP) This bit is based on all preceding bits
(device number, internal address, read/write and data
bits) and the parity bit itself. The parity -number of 1’s - of
all the preceding bits and the parity bit must be even - i.e.,
the result must be 0. During a read transaction, the EP bit
is sent by the LM95010 to the master to allow the master
to check the received data before using it.
• Acknowledge (ACK) During a read transaction the ACK
bit is sent by the master indicating that the EP bit was
received and was found to be correct, when compared to
the data preceding it, and that no conflict was detected
on the bus (excluding Attention Request - see Section
1.3.5 "Attention Request Transaction"). A read transfer is
considered "complete" only when the ACK bit is received.
A transaction that was not positively acknowledged is not
considered "complete" by the LM95010 and following are
performed:
— The BER bit in the LM95010 Device Status register is
set
— The LM95010 generates an Attention Request before,
or together with the Start Bit of the next transaction
A transaction that was not positively acknowledged is
also not considered "complete" by the master (i.e. inter-
nal operations related to the transaction are not per-
formed). The transaction may be repeated by the master,
after detecting the source of the Attention Request (the
LM95010 that has a set BER bit in the Device Status
register). Note that the SensorPath protocol neither
forces, nor automates re-execution of the transaction by
the master.
The values of the ACK bit are:
— 1: Data was received correctly
— 0: An error was detected (no-acknowledge).
1.3.3 Write Transaction
In a write transaction, the master writes data to a register at
a specified address in the LM95010. A write transaction
begins with a Start Bit and ends with an ACK Data Bit, as
show in Figure 8.
• Device Number This is the address of the slave device
accessed. Address "000" is a broadcast address and is
responded to by all the slave devices. The LM95010
responds to broadcast messages to the Device Control
Register.
• Internal Address This is the register address in the
LM95010 that will be written.
• Read/Write (R/W) A "0" data bit directs a write transac-
tion.
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FIGURE 6. Bus Reset Transaction
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FIGURE 7. Read Transaction, master reads data from LM95010
LM95010
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