18

NXP Semiconductors

33879

Figure 17. Parallel input SPI control

5.3

SPI definition

A 16-bit command word is sent to the 33879 on each SPI communication and a 16-bit status word is received from the 33879. The MSB

is sent and received first. As Table 7 shows, the Command Register defines the position and operation the 33879 performs on the rising

edge of CS. The Fault Register, shown in Table 8, defines the previous state status of the output driver. Table 9 identifies the type of fault

and the method by which the fault is communicated to the microprocessor

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.

0 = Bits 0 to 7, No Fault at Output.

1 = Bits 0 to 7, Output Short-to-Battery, Short-to-GND, Open Load, or TLIM.

Bits 8 to 15 will always return “0”.

Table 7. Command register definition

MSB

LSB

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

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

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

Table 8. Fault register definition

MSB

LSB

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

Bit 0

0

0

0

0

0

0

0

0

OUT 8

Status

OUT 7

Status

OUT 6

Status

OUT 5

Status

OUT 4

Status

OUT 3

Status

OUT 2

Status

OUT 1

Status

DI

DI

DI

SCLK

SCLK

SCLK

DO

DO

DO

CS

CS

CS

Parallel

Ports

MOSI

MISO

SCLK

8 Outputs

8 Outputs

8 Outputs

MC68HCxx

Microcontroller

with

SPI Interface

A

B

C

33879

33879

33879