Hardware manual

Rev. 3.0, 09/98, page 46 of 361
2.6.3 Power-Down State
The power-down state includes three modes: the sleep mode, the software standby mode, and the
hardware standby mode.
(1) Sleep Mode: The sleep mode is entered when a SLEEP instruction is executed. The CPU
halts, but CPU register contents remain unchanged and the on-chip supporting modules continue
to function.
(2) Software Standby Mode: The software standby mode is entered if the SLEEP instruction is
executed while the SSBY (Software Standby) bit in the system control register (SYSCR) is set.
The CPU and all on-chip supporting modules halt. The on-chip supporting modules are
initialized, but the contents of the on-chip RAM and CPU registers remain unchanged. I/O port
outputs also remain unchanged.
(3) Hardware Standby Mode: The hardware standby mode is entered when the input at the
STBY pin goes Low. All chip functions halt, including I/O port output. The on-chip supporting
modules are initialized, but on-chip RAM contents are held.
See section 14, “Power-Down State,” for further information.