TMS570LS3137 datasheet(129/159 Pages) TI

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NHET1

NHET2

NHET_LOOP_SYNC

EXT_LOOP_SYNC

NHET_LOOP_SYNC

TMS570LS3137

www.ti.com

SPNS162.

– SEPTEMBER 2011

Table 5-11. Dynamic Characteristics for the N2HET Input Capture Functionality

PARAMETER

MIN(1) (2)

MAX(1) (2)

UNIT

Input signal period, PCNT or WCAP for rising edge

2 (hr) (lr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

to rising edge

Input signal period, PCNT or WCAP for falling edge

2 (hr) (lr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

to falling edge

Input signal high phase, PCNT or WCAP for rising

(hr) (lr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

edge to falling edge

Input signal low phase, PCNT or WCAP for falling

(hr) (lr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

edge to rising edge

(1)

hr = High-resolution prescaler, configured using the HRPFC field of the Prescale Factor Register (HETPFR).

(2)

lr = Loop-resolution prescaler, configured using the LFPRC field of the Prescale Factor Register (HETPFR)

Both N2HET1 and N2HET2 have three channels each that are enhanced to be able to capture inputs with

smaller pulse widths than that specified in Table 5-11. These are N2HET1 channels 15, 20 and 31, and

N2HET2 channels 12, 14 and 16.

The input capture capability for these channels is specified in the following table.

Table 5-12. Input Capture Capability for N2HET Channels with Enhancements

PARAMETER

MIN

MAX

UNIT

Input signal period, PCNT or WCAP for rising edge

(hr) (lr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

to rising edge

Input signal period, PCNT or WCAP for falling edge

(hr) (lr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

to falling edge

Input signal high phase, PCNT or WCAP for rising

2 (hr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

edge to falling edge

Input signal low phase, PCNT or WCAP for falling

2 (hr) tc(VCLK2) + 2

225 (hr) (lr) tc(VCLK2) - 2

edge to rising edge

5.4.4

N2HET1-N2HET2 Interconnections

In some applications the N2HET resolutions must be synchronized. Some other applications require a

single time base to be used for all PWM outputs and input timing captures.

The N2HET provides such a synchronization mechanism. The Clk_master/slave (HETGCR.16) configures

the N2HET in master or slave mode (default is slave mode). A N2HET in master mode provides a signal

to synchronize the prescalers of the slave N2HET. The slave N2HET synchronizes its loop resolution to

the loop resolution signal sent by the master. The slave does not require this signal after it receives the

first synchronization signal. However, anytime the slave receives the re-synchronization signal from the

master, the slave must synchronize itself again..

Figure 5-6. N2HET1

– N2HET2 Synchronization Hookup

5.4.5

N2HET Checking

5.4.5.1

Internal Monitoring

To assure correctness of the high-end timer operation and output signals, the two N2HET modules can be

used to monitor each other

’s signals as shown in Figure 5-7. The direction of the monitoring is controlled

by the I/O multiplexing control module.

Peripheral Information and Electrical Specifications

129

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