P80C32 datasheet(5/20 Pages) TEMIC

5 / 20 page

80C32/80C52

Rev. G (14 Jan. 97)

MATRA MHS

PSEN

Program Store Enable output is the read strobe to external

Program Memory. PSEN is activated twice each machine

cycle during fetches from external Program Memory.

(However, when executing out of external Program

Memory, two activations of PSEN are skipped during

each access to external Data Memory). PSEN is not

activated during fetches from internal Program Memory.

PSEN can sink/source 8 LS TTL inputs. It can drive

CMOS inputs without an external pullup.

When EA is held high, the CPU executes out of internal

Program Memory (unless the Program Counter exceeds

1 FFFH). When EA is held low, the CPU executes only out

of external Program Memory. EA must not be floated.

XTAL1

Input to the inverting amplifier that forms the oscillator.

Receives the external oscillator signal when an external

oscillator is used.

XTAL2

Output of the inverting amplifier that forms the oscillator.

This pin should be floated when an external oscillator is

used.

Idle And Power Down Operation

Figure 3 shows the internal Idle and Power Down clock

configuration. As illustrated, Power Down operation

stops the oscillator. Idle mode operation allows the

interrupt, serial port, and timer blocks to continue to

function, while the clock to the CPU is gated off.

These special modes are activated by software via the

Special Function Register, PCON. Its hardware address is

87H. PCON is not bit addressable.

Figure 3.Idle and Power Down Hardware.

PCON : Power Control Register

(MSB)

(LSB)

SMOD

–

GF1

GF0

IDL

Symbol

Position

Name and Function

SMOD

PCON.7

Double Baud rate bit. When set to

a 1, the baud rate is doubled when

the serial port is being used in

either modes 1, 2 or 3.

–

PCON.6

(Reserved)

–

PCON.5

(Reserved)

–

PCON.4

(Reserved)

GF1

PCON.3

General-purpose flag bit.

GF0

PCON.2

General-purpose flag bit.

PCON.1

Power Down bit. Setting this bit

activates power down operation.

IDL

PCON.0

Idle mode bit. Setting this bit

activates idle mode operation.

If 1’s are written to PD and IDL at the same time. PD

takes, precedence. The reset value of PCON is

(000X0000).

Idle Mode

The instruction that sets PCON.0 is the last instruction

executed before the Idle mode is activated. Once in the

Idle mode the CPU status is preserved in its entirety : the

Stack Pointer, Program Counter, Program Status Word,

Accumulator, RAM and all other registers maintain their

data during idle. Table 1 describes the status of the

external pins during Idle mode.

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