LM93CIMT National Semiconductor, LM93CIMT Datasheet - Page 19

• Manufacturer Part Number: LM93CIMT
• Description: Microprocessor Support IC
• Manufacturer: National Semiconductor

Specifications of LM93CIMT

• Peak Reflow Compatible (260 C): No
• Supply Voltage Max: 3.6V
• Leaded Process Compatible: No
• Supply Voltage Min: 3V
• Operating Temperature Min: 0��C
• Package / Case: 56-TSSOP
• Operating Temperature Max: 85°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

14.0 SMBus Interface
telling the slave device to expect a block write, or it may
simply be a register address that tells the slave where sub-
sequent data is to be written.
Since data can flow in only one direction as defined by the
R/W bit, it is not possible to send a command to a slave
device during a read operation. Before doing a read opera-
tion, it is necessary to do a write operation to tell the slave
what sort of read operation to expect and/or the address
from which data is to be read.
When all data bytes have been read or written, stop condi-
tions are established. In WRITE mode, the master will allow
the data line to go high during the 10th clock pulse to assert
a STOP condition. In READ mode, the slave drives the data
not the master. For the bit in question, the slave is looking for
an acknowledge and the master doesn’t drive low. This is
known as ‘No Acknowledge’. The master then takes the data
line low during the low period before the 10th clock pulse,
then high during the 10th clock pulse to assert a STOP
condition.
Note, a repeated START may be given only between a write
and read operation that are in succession.
14.4 SMBUS ERROR SAFETY FEATURES
To provide a more robust SMBus interface, the LM93 incor-
porates a timeout feature for both SMBCLK and SMBDAT. If
either signal is low for a long period of time (see SMBus AC
specs), the LM93 SMBus state machine reverts to the idle
state and waits for a START signal. Large block transfers of
all zeros should be avoided if the SMBCLK is operating at a
very low frequency to avoid accidental timeouts. Pulling the
Reset pin low does not reset the SMBus state machine. If the
LM93 SMBDAT pin is low during a system reset, the LM93’s
state machine timeouts and resets automatically. If the
LM93’s SMBDAT pin is high during a system reset, the first
assertion of a start by the master resets the LM93’s interface
state machine.
Although it is a violation of the SMBus specification, in some
cases a START or STOP signal occurs in the middle of a
byte transfer instead of coming after an acknowledge bit. If
this occurs, only a partial byte was transferred. If a byte was
being written, it is aborted and the partial byte is not com-
mitted. If a byte was being read from a read-to-clear register,
the register is not cleared.
(Continued)
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14.5 SERIAL INTERFACE PROTOCOLS
The LM93 contains volatile registers, the registers occupy
address locations from 00h to EFh.
Data can be read and written as a single byte, a word, or as
a block of several bytes. The LM93 supports the following
SMBus/I
In addition to these transactions the LM93 supports a few
extra items and also has some behavior that must be defined
beyond the SMBus 2.0 specification. No other SMBus 2.0
transactions are supported (PEC, ARA etc.).
The SMBus specification defines several protocols for differ-
ent types of read and write operations. The ones used in the
LM93 are discussed below. The following abbreviations are
used in the diagrams:
S — START
P — STOP
R — READ
W — WRITE
A — ACKNOWLEDGE
/A — NO ACKNOWLEDGE
14.5.1 Address Incrementing
The established base address does not increment. Repeat-
edly reading without re-establishing a new base address
returns data from the same address each time. I
transactions can use this information and skip reestablishing
the base address, when only one master is used. One
exception to this rule exists when a block write and block
read is used to emulate a block write/read process call. This
is detailed later, see the Block Write/Read Process Call
description.
— Send Byte
— Write Byte
— Write Word
— SMBus Write Block
— I
— Read Byte
— Read Word
— SMBus Read Block
— SMBus Block-Write Block-Read Process Call
— I
2
2
C Block Write
C Block Read
2
C transactions/protocols:
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2
C read