Datasheet

Philips Semiconductors Product specification

80C51/87C51/80C52/87C52

80C51 8-bit microcontroller family

4 K/8 K OTP/ROM low voltage (2.7 V–5.5 V),

low power, high speed (33 MHz), 128/256 B RAM

2000 Aug 07

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

76543210

* 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)