Two-Wire Serial Interface Operation; Serial Read Operation - LSI Symbios SYM53C040 Technical Manual

2.6 Two-Wire Serial Interface Operation

Figure 2.8

Serial Read Operation

Control Byte
Device ID
R/W
Master
Bit
Slave ACK
Figure 2.9 Serial Write Operation
Control Byte
Device ID 0
R/W
Master
Bit
Slave
To enter ONCE mode, hold ALE low while bringing RESET/ to low, then
releasing it to high. ONCE mode should be used for testing or diagnostic
purposes only, and should be disabled during normal chip operation.
The Two-Wire Serial interface performs two main functions: it
automatically downloads firmware from an external serial EEPROM
device, and it serves as a Two-Wire Serial port with full multimaster and
slave capability that can communicate with external Two-Wire Serial
devices. The Two-Wire Serial interface in the SYM53C040 provides the
microcontroller an additional means to gather external system
information. The Two-Wire Serial interface supported by the SYM53C040
is compliant with the I
illustrates serial bus activity during a read operation.
serial bus activity during a write operation.
Address Byte
(1 or 2 Bytes)
0
ACK
Address Byte
ACK ACK
Two-Wire Serial Interface Operation
2
C bus defined by Philips Electronics.
Control Byte
Device ID
1 ACK
ACK
Data Byte
Data Byte
(More data
bytes may be
transferred,
each followed
by an ACK, up
to capacity of
slave device)
ACK
Figure 2.8
Figure 2.9 illustrates
(More data bytes
may be
transferred,
each followed by
an ACK)
Last Data Byte
Last Data Byte
No
ACK
ACK
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