MC68340 datasheet(110/441 Pages) FREESCALE

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MOTOROLA

MC68340 USER’S MANUAL

4- 13

Table 4-2. System Frequencies from 32.768-kHz Reference

W = 0; X = 0

W = 0; X = 1

W = 1; X = 0

W = 1; X = 1

000000

131

262

524

1049

000101

786

1573

3146

6291

001010

1442

2884

5767

11534

001111

2097

4194

8389

16777

010100

2753

5505

11010

22020

011001

3408

6816

13631

–

011111

4194

8389

16777

–

100011

4719

9437

18874

–

101000

5374

10748

21496

–

101101

6029

12059

24117

–

110010

6685

13369

–

110111

7340

14680

–

111100

7995

15991

–

111111

8389

16777

–

NOTE: System frequencies are in kHz.

4.2.3.3 CLOCK CONTROL. The clock control circuits determine the source used for both

internal and external clocks during special circumstances, such as low-power stop

(LPSTOP) execution.

Table 4-3 summarizes the clock activity during LPSTOP in crystal mode operation. Any

clock in the off state is held low. The STEXT and STSIM bits in the SYNCR control clock

activity during LPSTOP. Refer to 4.2.6 Low-Power Stop for additional information.

Table 4-3. Clock Control Signals

Control Bits

Clock Outputs

STSIM

STEXT

SIMCLK

CLKOUT

EXTAL

Off

EXTAL

VCO

Off

VCO

NOTE: SIMCLK runs the periodic interrupt

RESET and

IRQ

≈ pin synchronizers in LPSTOP mode.

4.2.4 Chip Select Operation

Typical microprocessor systems require external hardware to provide select signals to

external memory and peripherals. The MC68340 integrates these functions on chip to

provide the cost, speed, and reliability benefits of a higher level of integration. The chip

select function contains register pairs for each external chip select signal. The pair

consists of a base address register and an address mask register that define the

characteristics of a single chip select. The register pair provides flexibility for a wide

variety of chip select functions.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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