DP8344 datasheet(11/184 Pages) NSC

11 / 184 page

10 Communications Processor Introduction (Continued)

14 DATA FLOW

The CPU registers are all dual port that is they have sepa-

rate input and output paths This arrangement allows a sin-

gle register to function as both a source and a destination

within the same instruction

Figures 1-6a through 1-6f show the internal data flow path

for the BCP The CPU registers are a central element to this

path When a register functions as an output its contents

are placed on the Source bus When a register is an input

data from the Destination bus is written into that register

The other key element in the data path is the ALU This unit

does all of the arithmetic and data manipulation operations

but it also has bus multiplexing capabilities Both the Data

Memory bus and a portion of the Instruction Memory bus

are routed to this unit and serve as alternative sources of

data Since the data flow is always through this unit most

data moves may include arithmetic manipulations with no

penalty in execution time

Figure 1-6a shows the data path for all arithmetic instruc-

tions and register to register moves The source register

contents are placed on the Source bus routed through the

TLF9336 – C3

TLF9336 – C4

TLF9336 – C5

FIGURE 1-6a Register to Register

FIGURE 1-6b Data Memory WRITE

FIGURE 1-6c Data Memory READ

TLF9336 – C6

TLF9336 – C7

TLF9336 – C8

FIGURE 1-6d WRITE to Transmitter

FIGURE 1-6e READ from Receiver

FIGURE 1-6f Load Immediate Data

DP8344 Datasheet(PDF) 11 Page - National Semiconductor (TI)