Texas Instruments TMS3320C5515

Power Management

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1.5.3.2.2 Peripheral Clock Stop Request/Acknowledge Register (CLKSTOP) [1C3Ah]

You must execute a handshaking procedure before stopping the clock to the EMIF, USB, and UART. This

handshake procedure ensures that current bus transactions are completed before the clock is stopped.

The peripheral clock stop request/acknowledge register (CLKSTOP) enables this handshaking

mechanism.

To stop the clock to the EMIF, USB, or UART, set the corresponding clock stop request bit in the

CLKSTOP register, then wait for the peripheral to set the corresponding clock stop acknowledge bit. Once

this bit is set, you can idle the corresponding clock in the PCGCR1 and PCGCR2.

To enable the clock to the EMIF, USB, or UART, first enable the clock the peripheral through PCGCR1 or

PCGCR2, then clear the corresponding clock stop request bit in the CLKSTOP register.

The peripheral clock stop request/acknowledge register (CLKSTOP) is shown in Figure 1-16 and

described in Table 1-26.

Figure 1-16. Peripheral Clock Stop Request/Acknowledge Register (CLKSTOP) [1C3Ah]

15 8

Reserved

R-0

76543210

Reserved URTCLKSTPACK URTCLKSTPREQ USBCLKSTPACK USBCLKSTPREQ EMFCLKSTPACK EMFCLKSTPREQ

R-0 R-1 R/W-1 R-1 R/W-1 R-1 R/W-1

LEGEND:R/W = Read/Write; R = Read only; -n= value after reset

Table 1-26. Peripheral Clock Stop Request/Acknowledge Register (CLKSTOP) Field Descriptions

Bit Field Value Description

15-6 Reserved 0 Reserved.

5 URTCLKSTPACK UARTclock stop acknowledge bit. This bit is set to 1 when the UART has acknowledged

arequest for its clock to be stopped. The UART clock should not be stopped until this bit

isset to 1.

0 Therequest to stop the peripheral clock has not been acknowledged.

1 Therequest to stop the peripheral clock has been acknowledged, the clock can be

stopped.

4 URTCLKSTPREQ UARTperipheral clock stop request bit. When disabling the UART internal peripheral

clock,you must set this bit to 1 to request permission to stop the clock. After the UART

acknowledgesthe request (URTCLKSTPACK = 1) you can stop the clock through the

peripheralclock gating control register 1 (PCGCR1). When enabling the UART internal

clock,enable the clock through PCGCR1, then set URTCKLSTPREQ to 0.

0 Normaloperating mode.

1 Requestpermission to stop the peripheral clock.

3 USBCLKSTPACK USBclock stop acknowledge bit. This bit is set to 1 when the USB has acknowledged a

requestfor its clock to be stopped. The USB clock should not be stopped until this bit is

setto 1.

0 Therequest to stop the peripheral clock has not been acknowledged.

1 Therequest to stop the peripheral clock has been acknowledged, the clock can be

stopped.

2 USBCLKSTPREQ USBperipheral clock stop request bit. When disabling the USB internal peripheral clock,

youmust set this bit to 1 to request permission to stop the clock. After the USB

acknowledgesthe request (USBCLKSTPACK = 1) you can stop the clock through the

peripheralclock gating control register 2 (PCGCR2). When enabling the USB internal

clock,enable the clock through PCGCR2, then set USBCKLSTPREQ to 0.

0 Normaloperating mode.

1 Requestpermission to stop the peripheral clock.

42 SystemControl SPRUFX5A–October 2010 –Revised November 2010

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