33879 Datasheet, PDF (17/24 Pages) Freescale Semiconductor, Inc – Configurable Octal Serial Switch with Open Load Detect Current Disable

FUNCTIONAL DESCRIPTION
SPI DEFINITION
MOSI
SCLK
MISO
MC68HCxx
Microcontroller
with
SPI Interface
33879
DI
SCLK
DO
CS
33879
DI
SCLK
DO
CS
8 Outputs
8 Outputs
A
Parallel
Ports
B
C
33879
DI
SCLK
DO
CS
Figure 17. Parallel Input SPI Control
8 Outputs
SPI DEFINITION
On each SPI communication, a 16-bit command word is
sent to the 33879 and a 16-bit status word is received from
the 33879. The MSB is sent and received first. As Table 6
shows, the Command Register defines the position and
operation the 33879 will perform on rising edge of CS. The
Fault Register, shown in Table 7, defines the previous state
status of the output driver. Table 8 identifies the type of fault
and the method by which the fault is communicated to the
microprocessor.
Table 6. Command Register Definition
MSB
Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
Bit 0
ON /
OFF
Open
Load
Detect
8
ON /
OFF
Open
Load
Detect
7
ON /
OFF
Open
Load
Detect
6
ON /
OFF
Open
Load
Detect
5
ON /
OFF
Open
Load
Detect
4
ON /
OFF
Open
Load
Detect
3
ON /
OFF
Open
Load
Detect
2
ON /
OFF
Open
Load
Detect
1
0 = Bits 0 to 7, Output commanded OFF.
0 = Bits 8 to 15, Open Load Detection Current OFF.
ON /
OFF
OUT 8
ON /
OFF
OUT 7
ON /
OFF
OUT 6
ON /
OFF
OUT 5
ON /
OFF
OUT 4
ON /
OFF
OUT 3
ON /
OFF
OUT 2
ON /
OFF
OUT 1
1 = Bits 0 to 7, Output commanded ON.
1 = Bits 8 to 15 Open Load Detection Current ON.
Table 7. Fault Register Definition
MSB
Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
LSB
Bit 0
0
0
0
0
0
0
0
0
0 = Bits 0 to 7, No Fault at Output.
1 = Bits 0 to 7, Output Short-to-Battery, Short-to-GND,
Open Load, or T_LIM.
OUT 8 OUT 7 OUT 6 OUT 5 OUT 4 OUT 3
Status Status Status Status Status Status
Bits 8 to 15 will always return “0”.
OUT 2
Status
OUT 1
Status
Analog Integrated Circuit Device Data
Freescale Semiconductor
33879
17