33879_09 Datasheet, PDF (16/23 Pages) Freescale Semiconductor, Inc – Configurable Octal Serial Switch with Open Load Detect Current Disable

FUNCTIONAL DESCRIPTION
SPI DEFINITION
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
shows, the Command Register defines the position and
operation the 33879 will perform on rising edge of CS. The
Fault Register, shown in Table 6, defines the previous state
status of the output driver. Table 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 / ON / ON / ON / ON / ON / ON / ON / ON / ON / ON / ON / ON / ON / ON / ON /
OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF OFF
Open Open Open Open Open Open Open Open OUT 8 OUT 7 OUT 6 OUT 5 OUT 4 OUT 3 OUT 2 OUT 1
Load Load Load Load Load Load Load Load
Detect Detect Detect Detect Detect Detect Detect Detect
8
7
6
5
4
3
2
1
0 = Bits 0 to 7, Output commanded OFF.
0 = Bits 8 to 15, Open Load Detection Current OFF.
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 OUT 8 OUT 7 OUT 6 OUT 5 OUT 4 OUT 3 OUT 2 OUT 1
Status Status Status Status Status Status Status Status
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.
Bits 8 to 15 will always return “0”.
Table 8. Fault Operation
Serial Output (DO) Pin Reports
Over-temperature
Fault reported by serial output (DO) pin.
Over-current
DO pin reports short to battery/supply or over-current condition.
Output ON Open Load Fault
Not reported.
Output OFF Open Load Fault
DO pin reports output OFF open load condition only with Open Load Detection Current enabled.
DO pin will report “0” for Output OFF Open Load Fault with Open Load Detection Current disabled.
Device Shutdowns
Over-voltage
Total device shutdown at V_PWR = V_PWR(OV) V. Resumes normal operation with proper voltage. All
outputs assuming the previous state upon recovery from over-voltage.
Over-temperature
Only the output experiencing an over-temperature shuts down. Output assumes previous state upon
recovery from over-temperature.
33879
16
Analog Integrated Circuit Device Data
Freescale Semiconductor