Motorola DSP56012 User Manual

The DSP56012 on-chip peripheral memory map is illustrated in 

 and in 

. 

The standard MOVE instruction transfers data between Port B and a register. As a 
result, MOVE takes two instructions to perform a memory-to-memory data transfer 
and uses a temporary holding register. The MOVEP instruction is specifically 
designed for I/O data transfer, as shown in 

instruction can take twice as long to execute as a MOVE instruction, only one 
MOVEP is required for a memory-to-memory data transfer, and MOVEP does not 
use a temporary register. Using the MOVEP instruction allows a fast interrupt to 
move data to/from a peripheral or from/to memory and execute one other 
instruction or move the data to an absolute address. MOVEP is the only 
memory-to-memory move instruction. However, one of the memory operands must 
be in the top sixty-four locations of either X: or Y: memory, which are reserved for 
internal and external I/O, respectively.

The bit-oriented instructions that use I/O short addressing (BCHG, BCLR, BSET, 
BTST, JCLR, JSCLR, JSET, and JSSET) can also address individual bits for faster I/O 
processing. The DSP does not have a hardware data strobe to move data out of the 
GPIO port. If a strobe is needed, use software to toggle one of the GPIO pins to 
emulate a strobe signal.

Generally, it is not good programming practice to activate a peripheral before 
programming it. Thus, even though reset initializes the Port B as fifteen GPIO inputs, 
it is best to configure Port B as GPIO inputs explicitly, and then configure the data 
direction and data registers. However, some situations may require programming 
the data direction or the data registers first to prevent two devices from driving one 
signal. The order of steps 1, 2, and 3 in 

needed.

Figure 4-5  Instructions to Write/Read Parallel Data with Port B

•

MOVE

#$0,X:$FFEC

;Select Port B to be

;GPIO

MOVE

#$7F00,X:$FFED

;Select pins PB0–PB7 to be inputs

•

;and pins PB8–PB14 to be outputs

•

MOVEP

#data_out,X:$FFEE

;Put bits 8–14 of “data_out” on pins

;PB8–PB14, bits 0–7 are ignored.

MOVEP

X:$FFEE,#data_in

;Put PB0–PB7 in bits 0–7 of “data_in”