Philips Semiconductors

Product specification

80C51/87C51/80C31

80C51 8-bit microcontroller family

4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V),

low power, high speed (33 MHz)

2000 Jan 20

11

Not Bit Addressable

Symbol

Function

—

Not implemented, reserved for future use.*

T2OE

Timer 2 Output Enable bit.

DCEN

Down Count Enable bit. When set, this allows Timer 2 to be configured as an up/down counter.

—

—

—

—

—

—

T2OE

DCEN

SU00729

76

54

32

1

0

*

User software should not write 1s to reserved bits. These bits may be used in future 8051 family products to invoke new features.

In that case, the reset or inactive value of the new bit will be 0, and its active value will be 1. The value read from a reserved bit is

indeterminate.

Bit

T2MOD

Address = 0C9H

Reset Value = XXXX XX00B

Figure 3. Timer 2 Mode (T2MOD) Control Register

OSC

÷ 12

C/T2 = 0

C/T2 = 1

TR2

CONTROL

TL2

(8-BITS)

TH2

(8-BITS)

TF2

RCAP2L

RCAP2H

EXEN2

CONTROL

EXF2

TIMER 2

INTERRUPT

T2EX PIN

TRANSITION

DETECTOR

T2 PIN

RELOAD

SU00067

Figure 4. Timer 2 in Auto-Reload Mode (DCEN = 0)