Motorola DSP56012 User Manual

The process to execute an HC (see 

1. The host processor writes the CVR with the desired HV (the HV is the DSP’s 

interrupt vector (IV) location divided by two, i.e., if HV = $17, IV = $34).

2. The HC bit is then set.

3. The HCP bit in the HSR is set when the HC bit is set.

4. If the HCIE bit in the HCR has been set by the DSP, the HC interrupt 

processing will start. The HV is multiplied by 2 and the result is used by the 
DSP as the interrupt vector.

5. When the HC interrupt is acknowledged, the HC bit (and therefore the HCP 

bit) is cleared by the HC logic. HC can be read by the host processor as a status 
bit to determine when the command is accepted. Similarly, the HCP bit can be 
read by the DSP CPU to determine if an HC is pending.

To guarantee a stable interrupt vector, write HV only when HC is clear. The HC bit 
and HV can be written simultaneously. The host processor can clear the HC bit to 
cancel a host command at any time before the DSP interrupt is accepted. Although 
the HV can be programmed to any interrupt vector, it is not recommended that 
HV = 0 (RESET) be used because it does not reset the DSP hardware. DMA must be 
disabled to use the host interrupt.

Figure 4-28  Receive Data from Host—Main Program

Figure 4-29  Receive Data from Host Interrupt Routine

;****************************************

; MAIN PROGRAM... receive data from host

;****************************************

ORG

P:$80

MOVE

#0,R0

MOVE

#3,M0

MOVEP

#1,X:PBC

;Enable HI

MOVEP

#0,X:HCR

;Turn off XMT and RCV interrupts

MOVEP

#$0C00,X:IPR

;Turn on host interrupt

MOVE

#0,SR

;Unmask interrupts

JCLR

#3,X:HSR,*

;Wait for HF0 (from host) set

MOVEP

#$1,X:HGR

;Enable host receive interrupt

JMP

*

;Now wait for interrupt

;************************************

; Receive from Host Interrupt Routine

;************************************

MOVEP

X:HORX,X:(R0)+;Receive data.

RTI 

END