Motorola DSP56012 User Manual

The Serial Host Interface (SHI) is a serial I/O interface that provides a path for 
communication and program/coefficient data transfers between the DSP and an 
external host processor. The SHI can also communicate with other serial peripheral 
devices. The SHI can interface directly to either of two well-known and widely used 
synchronous serial buses: the Motorola Serial Peripheral Interface (SPI) bus and the 
Philips Inter-Integrated-circuit Control (I

2

C) bus. The SHI supports either the SPI or 

I

2

C bus protocol, as required, from a slave or a single-master device. To minimize 

DSP overhead, the SHI supports single-, double-, and triple-byte data transfers. The 
SHI has a 10-word receive FIFO that permits receiving up to 30 bytes before 
generating a receive interrupt, reducing the overhead for data reception.

When configured in the SPI mode, the SHI can:

• Identify its slave selection (in Slave mode)

• Simultaneously transmit (shift out) and receive (shift in) serial data

• Directly operate with 8-, 16- and 24-bit words

• Generate vectored interrupts, separately for receive and transmit events, and 

update status bits

• Generate a separate vectored interrupt in the event of a receive exception

• Generate a separate vectored interrupt in the event of a bus-error exception

• Generate the serial clock signal (in Master mode)

When configured in the I

2

C mode, the SHI can:

• Detect/generate start and stop events

• Identify its slave (ID) address (in Slave mode) 

• Identify the transfer direction (receive/transmit)

• Transfer data byte-wise according to the SCL clock line

• Generate ACK signal following a byte receive

• Inspect ACK signal following a byte transmit

• Directly operate with 8-, 16- and 24-bit words 

• Generate vectored interrupts separately for receive and transmit events and 

update status bits

• Generate a separate vectored interrupt in the event of a receive exception

• Generate a separate vectored interrupt in the event of a bus error exception

• Generate the clock signal (in Master mode)