L6238 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6238' PDF : 35 Pages View PDF
6.1 Description
The L6238 contains a powerful serial port that
may be optionally used to dramatically increase
the functionality of the controller without signifi-
cantly increasing the pin count. The serial port
serves two primary functions:
1. Receive Control Information
A total of 16 bits of control information can be pro-
grammed via the serial port, in addition to the ca-
pabilities provided by external pins. By duplicating
key serial port control functions at dedicated pins,
the L6238 will still provide sufficient motor control
for many applications, without the use of the se-
rial port.
2. Provide Status Information
Certain status information is available only via the
serial port, with additional information available at
dedicated pins.
6.2 Block Diagram
Figure 29 is a simplified block diagram of the
serial port. It consists of a 16-bit shift register, a
16-bit latch, and some control logic. The serial
port utilizes 5 pins to communicate with the out-
side world. They are:
Data I/O The data I/O pin enables 16 bits of data
to flow in as control or out as status information.
Read/Write This pin selects read or write mode.
Clock Used to shift data in or out of the serial
Figure 29: Block Diagram.
L6238
port.
Disable If multiple controllers are connected for
parallel operation, this signal can be used to se-
lect communication to a particular port. If the Se-
rial Port is not used, the PORT DISABLE pin
should be tied high.
Strobe The read operation is transparent. When
the strobe is high, the data on the status bus
flows through to the serial register. In a write op-
eration, the loading of the control bits into the par-
allel control latch is an edge-triggered operation
occurring on the rising edge of the strobe.
6.3 Functional Truth Table
Table 4 defines the states for the disable and
R/W functions. If the disable pin is asserted high,
the Data I/O pin is tristated to a High-Impedance
state. The R/W pin determines whether the Data
I/O pin is an input or an output.
The AC operating parameters of the serial port
are defined in the Electrical Specifications.
Table 4: Truth Table.
Dis R/W
Function
0
0 Write to Serial Port (Data I/O = Input)
0
1 Read to Serial Port (Data I/O = Output)
1
X Chip Disabled (Data I/O = Hi Z)
6.4 Timing Diagrams
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