Motorola DSP56309 User Manual page 148

The CVR is a special command register by which the host processor issues commands to
the DSP56309. Only the host processor can access this register.
Host processors can use standard host processor instructions (e.g., byte move) and
addressing modes to communicate with the HI08 registers. The HI08 registers are
aligned so that 8-bit host processors can use 8/16/24-bit load and store instructions for
data transfers. The HREQ/HTRQ and HACK/HRRQ handshake flags are provided for
polled or interrupt-driven data transfers with the host processor. Because of the speed of
the DSP56309 interrupt response, most host microprocessors can load or store data at
their maximum programmed I/O instruction rate without testing the handshake flags
for each transfer. If full handshake is not needed, the host processor can treat the
DSP56309 as a fast device, and data can be transferred between the host processor and
the DSP56309 at the fastest host processor data rate.
One of the most innovative features of the host interface is the host command feature.
With this feature, the host processor can issue vectored interrupt requests to the
DSP56309. The host can select any of 128 DSP interrupt routines for execution by writing
a vector address register in the HI08. This flexibility allows the host processor to execute
up to 128 pre-programmed functions inside the DSP56309. For example, use of the
DSP56309 host interrupts can allow the host processor to read or write DSP registers (X,
Y, or program memory locations), force interrupt handlers (e.g., SSI, SCI, IRQA, IRQB
interrupt routines), and perform control and debugging operations.
Note: When the DSP enters stop mode, the HI08 signals are electrically disconnected
internally, thus disabling the HI08 until the core leaves stop mode. While the
HI08 configuration remains unchanged in stop mode, the core cannot be
restarted via the HI08 interface.
Do not issue a STOP command to the DSP via the HI08 unless some other
mechanism for exiting stop mode is provided.
MOTOROLA
HI08-External Host ProgrammerÕs Model
DSP56309UM/D
Host Interface (HI08)
6-21