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Program-Address Generation
5-2
5.1 Program-Address Generation
Program flow requires the processor to generate the next program address
(sequential or nonsequential) while executing the current instruction. Pro-
gram-address generation is illustrated in Figure 5–1 and summarized in
Table 5–1.
Figure 5–1. Program-Address Generation Block Diagram
Interrupt,
branch, or call
MUX
Next program address
register (NPAR)
Program counter
(PC/NPAR+1)
Sequential operation
Program address
register (PAR)
Dummy cycle
Micro stack
(MSTACK)
Table/block move
MUX
Program read bus (PRDB)
Data read bus (DRDB)
Top of stack (TOS)
Program-address
stack
8 16
Program address bus (PAB)
Data write bus (DWEB)
PSHD
instruction
Return
from
subroutine
POPD
instruction
Program
control
BACC or CALA
instruction