Texas Instruments TMS3320C5515 manual Urtclkstpack, Urtclkstpreq, Usbclkstpack, Usbclkstpreq

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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 1-16and described in Table 1-26.

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

15							8
				Reserved
				R-0
7	6	5	4	3	2	1	0

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		UART clock stop acknowledge bit. This bit is set to 1 when the UART has acknowledged
			a request for its clock to be stopped. The UART clock should not be stopped until this bit
			is set to 1.
		0	The request to stop the peripheral clock has not been acknowledged.
		1	The request to stop the peripheral clock has been acknowledged, the clock can be
			stopped.
4	URTCLKSTPREQ		UART peripheral 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
			acknowledges the request (URTCLKSTPACK = 1) you can stop the clock through the
			peripheral clock gating control register 1 (PCGCR1). When enabling the UART internal
			clock, enable the clock through PCGCR1, then set URTCKLSTPREQ to 0.
		0	Normal operating mode.
		1	Request permission to stop the peripheral clock.
3	USBCLKSTPACK		USB clock stop acknowledge bit. This bit is set to 1 when the USB has acknowledged a
			request for its clock to be stopped. The USB clock should not be stopped until this bit is
			set to 1.
		0	The request to stop the peripheral clock has not been acknowledged.
		1	The request to stop the peripheral clock has been acknowledged, the clock can be
			stopped.
2	USBCLKSTPREQ		USB peripheral clock stop request bit. When disabling the USB internal peripheral clock,
			you must set this bit to 1 to request permission to stop the clock. After the USB
			acknowledges the request (USBCLKSTPACK = 1) you can stop the clock through the
			peripheral clock gating control register 2 (PCGCR2). When enabling the USB internal
			clock, enable the clock through PCGCR2, then set USBCKLSTPREQ to 0.
		0	Normal operating mode.
		1	Request permission to stop the peripheral clock.

42	System Control	SPRUFX5A –October 2010 –Revised November 2010
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