Z380 Datasheet, PDF (42/115 Pages) Zilog, Inc. – MICROPROCESSOR

ZILOG
CPU ARCHITECTURE (Continued)
XM (Extended Mode). This bit controls the Extended/
Native mode selection for the Z380 CPU. This bit is set by
the SETC XM instruction, and once set, it can be cleared
only by a reset on the /RESET pin. When this bit is set, the
Z380 CPU is in Extended mode. Reset clears this bit and
the Z380 CPU is in Native mode.
LW (Long Word Mode). This bit controls the Long Word/
Word mode selection for the Z380 CPU. This bit is set by
the SETC LW instruction and cleared by the RESC LW
instruction. When this bit is set, the Z380 CPU is in Long
Word mode; when this bit is cleared, the Z380 CPU is in
Word mode. Reset clears this bit. Note that individual
instructions may be executed in either Word or Long Word
load and exchange mode, using the DDIR W and DDIR LW
decoder directives.
IEF1 (Interrupt Enable Flag). This bit is the master Interrupt
Enable for the Z380 CPU. This bit is set by the EI instruction
and cleared by the DI instruction. When this bit is set,
interrupts are enabled; when this bit is cleared, interrupts
are disabled. Reset clears this bit.
MICROPROCESSOR
IM (Interrupt Mode). This 2-bit field controls the interrupt
mode for the /INT0 interrupt request. These bits are
controlled by the IM instructions (00 = IM 0, 01 = IM 1,
10 = IM 2, 11 = IM 3). Reset clears both of these bits,
selecting Interrupt Mode 0.
LCK (Lock). This bit controls the Lock/ Unlock status of the
Z380 CPU. This bit is set by the SETC LCK instruction and
cleared by the RESC LCK instruction. When this bit is set,
no bus requests are accepted, providing exclusive ac-
cess to the bus by the Z380 CPU. When this bit is cleared
the Z380 CPU will grant bus requests in the normal fashion.
Reset clears this bit.
AFP (AF Prime Register Select). This bit controls and
reports whether AF or AF' is the currently active pair of
registers. AF is selected when this bit is cleared and AF' is
selected when this bit is set. Reset clears this bit and
selects AF.
PS010001-0301