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5.6.4

Clock Generation in Lock Mode (APLL Synthesis Enabled)

N +

TMS320VC5502

Fixed-Point Digital Signal Processor

SPRS166H – APRIL 2001 – REVISED NOVEMBER 2004

The frequency of the reference clock provided at the CLKIN pin can be multiplied by a synthesis factor of N to

generate the internal CPU clock cycle. The synthesis factor is determined by:

where:

• M = the multiply factor set in the PLLM field of the PLL Multiplier Control Register (PLLM)

• D

0 = the divide factor set in the PLLDIV0 field of the PLL Divider 0 Register (PLLDIV0)

Valid values for M are (multiply by) 2 to 15. Valid values for D0 are (divide by) 1 – 32.

For detailed information on clock generation configuration, see Section 3.10, System Clock Generator.

Table 5-4 and Table 5-5 assume testing over recommended operating conditions and H = 0.5tc(CO) (see

Figure 5-4).

Table 5-4. CLKIN in Lock Mode Timing Requirements

VC5502-200

VC5502-300

NO.

UNIT

MIN

MAX

tc(CI)

Cycle time, CLKIN(1)

APLL synthesis enabled

10(2)

83.3

tf(CI)

Fall time, CLKIN

tr(CI)

Rise time, CLKIN

(1)

If an external crystal is used, the X2/CLKIN cycle time is limited by the crystal frequency range listed in Table 5-1.

(2)

The clock frequency synthesis factor and minimum CLKIN cycle time should be chosen such that the resulting CLKOUT cycle time is

within the specified range [tc(CO)].

Table 5-5. CLKOUT in Lock Mode Switching Characteristics

VC5502-200

VC5502-300

NO.

PARAMETER

UNIT

MIN

TYP

MAX

tc(CO)

Cycle time, CLKOUT

6.66

K * tc(CI)/N(1)

14.29

tf(CO)

Fall time, CLKOUT

tr(CO)

Rise time, CLKOUT

tw(COL)

Pulse duration, CLKOUT low

K * tc(CI) /2N – 1

K * tc(CI) /2N + 1

tw(COH)

Pulse duration, CLKOUT high

K * tc(CI) /2N – 1

K * tc(CI) /2N + 1

(1)

N = Clock frequency synthesis factor. K = divider ratio between CPU clock and system clock selected as CLKOUT. For example, when

SYSCLK1 is selected as CLKOUT and SYSCLK1 is set to the CPU clock divided by four, use K = 4.

133

Specifications

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