80C32/80C52
MATRA MHS
There are three ways to terminate the Idle mode.
Activation of any enabled interrupt will cause PCON.0 to
be cleared by hardware, terminating Idle mode. The
interrupt is serviced, and following RETI, the next
instruction to be executed will be the one following the
instruction that wrote 1 to PCON.0.
Power Down Mode
The instruction that sets PCON.1 is the last executed prior
to entering power down. Once in power down, the
oscillator is stopped. The contents of the onchip RAM and
the Special Function Register is saved during power down
mode. The hardware reset initiates the Special Fucntion
Register. In the Power Down mode, VCC may be lowered
to minimize circuit power consumption. Care must be
taken to ensure the voltage is not reduced until the power
down mode is entered, and that the voltage is restored
before the hardware reset is applied which freezes the
oscillator. Reset should not be released until the oscillator
has restarted and stabilized.
The flag bits GF0 and GF1 may be used to determine
whether the interrupt was received during normal
execution or during the Idle mode. For example, the
instruction that writes to PCON.0 can also set or clear one
or both flag bits. When Idle mode is terminated by an
enabled interrupt, the service routine can examine the
status of the flag bits.
Table 1 describes the status of the external pins while in
The second way of terminating the Idle mode is with a
hardware reset. Since the oscillator is still running, the the power down mode. It should be noted that if the power
hardware reset needs to be active for only 2 machine down mode is activated while in external program
cycles (24 oscillator periods) to complete the reset memory, the port data that is held in the Special Function
Register P2 is restored to Port 2. If the data is a 1, the port
pin is held high during the power down mode by the
strong pullup, T1, shown in Figure 4.
operation.
Table 1 : Status of the external pins during idle and power down modes.
MODE
Idle
PROGRAM MEMORY
ALE
PSEN
PORT0
Port Data
Floating
Port Data
Floating
PORT1
Port Data
Port Data
Port Data
Port Data
PORT2
Port Data
Address
PORT3
Port Data
Port Data
Port Data
Port Data
Internal
External
Internal
External
1
1
0
0
1
1
0
0
Idle
Power Down
Power Down
Port Data
Port Data
Figure 4. I/O Buffers in the 80C52 (Ports 1, 2, 3).
Stop Clock Mode
Due to static design, the MHS 80C32/C52 clock speed
can be reduced until 0 MHz without any data loss in
memory or registers. This mode allows step by step
utilization, and permits to reduce system power
consumption by bringing the clock frequency down to
any value. At 0 MHz, the power consumption is the same
as in the Power Down Mode.
I/O Ports
The I/O buffers for Ports 1, 2 and 3 are implemented as
shown in figure 4.
6
Rev. E (31/08/95)