Functionally, the CHMOS devices (designated with “C” in the middle of the device name) me all fiuy compatible with the 8051, but being CMOS, draw less current than an HMOS counterpart. To further exploit the power savings available in CMOS circuitry, two re- duced power modes are added l Software-invoked Idle Mode, during which the CPU is turned off while the RAM and other on-chip peripherals continue operating. In this mode, cur- rent draw is reduced to about 15% of the current drawn when the device is fully active. l Software-invoked Power Down Mode, during which all on-chip activities are suspended. The on-chip RAM continues to hold its data. In this mode the device.
