DS80C310

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PERIPHERAL OVERVIEW

The DS80C310 provides the same peripheral functions as the standard 80C32. The device is compatible

with the DS80C320, but it does not offer all the peripherals.

TIMER RATE CONTROL

There is one important difference between the DS80C310 and 8051 regarding timers. The original 8051

used 12 clocks per cycle for timers and machine cycles. The DS80C310 architecture normally uses 4

clocks per machine cycle. However, in the area of timers and serial ports, the DS80C310 defaults to 12

clocks per cycle on reset. This allows existing code with real-time dependencies such as baud rates to

operate properly.

If an application needs higher speed timers or serial baud rates, the user can select individual timers to run

at the 4-clock rate. The Clock Control Register (CKCON; 8Eh) determines these timer speeds. When the

relevant CKCON bit is logic 1, the DS80C310 uses 4 clocks per cycle to generate timer speeds. When the

bit is 0, the DS80C310 uses 12 clocks for timer speeds. The reset condition is 0. CKCON.5 selects the

speed of Timer 2. CKCON.4 selects Timer 1 and CKCON.3 selects Timer 0. Note that unless a user

desires very fast timing, it is unnecessary to alter these bits. Also note that the timer controls are

independent.

POWER-ON RESET

The DS80C310 holds itself in reset during a power-up until 65,536 clock cycles have elapsed. The power-

on reset used by the DS80C310 differs somewhat from other members of the high-speed microcontroller

family. The crystal oscillator can start anywhere between 1.0V and 4.5V, but is not specified. This

eliminates the need for an RC reset circuit. For voltage-specific precision-brownout detection, an external

component is needed. When the device goes through a power-on reset, the POR flag is set in the

WDCON (D8h) register at bit 6.

INTERRUPTS

The DS80C310 provides 10 interrupt sources with two priority levels. Software can assign high or low

priority to all sources. All interrupts that are new to the 8051 have a lower natural priority than the

originals.

Table 3. Interrupt Sources and Priorities

NAME

DESCRIPTION

VECTOR

NATURAL

PRIORITY

INT0

External Interrupt 0

03h

1

TF0

Timer 0

0Bh

2

INT1

External Interrupt 1

13h

3

TF1

Timer 1

1Bh

4

SCON

T1 or R1 from the serial port

23h

5

TF2

Timer 2

2Bh

6

INT2

External Interrupt 2

43h

7

INT3

External Interrupt 3

4Bh

8

INT4

External Interrupt 4

53h

9

INT5

External Interrupt 5

5Bh

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