Texas Instruments TMS320C6457 manual HCNTL10 and HR/W Indicating the Cycle Type

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3.4HCNTL[1:0] and HR/W: Indicating the Cycle Type

The cycle type consists of:

•The access type selected by the host by driving the appropriate levels on the HCNTL[1:0] pins of the HPI. Table 4 describes the four available access types.

•The transfer direction that the host selects with the HR/W pin. The host must drive the HR/W signal high (read) or low (write).

Table 5 summarizes the cycle types. The HPI samples the HCNTL levels either at the falling edge of HAS (if HAS is used) or at the falling edge of the internal strobe signal HSTRB (if HAS is not used or is tied high).

CAUTION

Note that the encoding of HCNTL0 and HCNTL1 for the different types of HPI accesses varies on many TI DSPs; therefore, you should use caution to ensure that the correct encoding of these inputs is used for your device. The encoding of these signals as described in this document applies only to C6457 DSPs.

Table 4. Access Types Selectable by the HCNTL Signals

HCNTL1	HCNTL0	Description
0	0	HPIC access. The host requests to access the HPI control register
		(HPIC).
0	1	HPID access with autoincrementing. The host requests to access the
		HPI data register (HPID) and to have the appropriate HPI address
		register (HPIAR and/or HPIAW) automatically incremented by 1 after
		the access.
1	0	HPIA access. The host requests to access the appropriate HPI
		address register (HPIAR and/or HPIAW).
1	1	HPID access without autoincrementing. The host requests to access
		the HPI data register (HPID) but requests no automatic
		post-increment of the HPI address register.

Table 5. Cycle Types Selectable With the HCNTL and HR/W Signals

HCNTL1	HCNTL0	HR/W	Cycle Type
0	0	0	HPIC write cycle
0	0	1	HPIC read cycle
0	1	0	HPID write cycle with autoincrementing
0	1	1	HPID read cycle with autoincrementing
1	0	0	HPIA write cycle
1	0	1	HPIA read cycle
1	1	0	HPID write cycle without
			autoincrementing
1	1	1	HPID read cycle without
			autoincrementing

16 Host Port Interface (HPI) SPRUGK7A –March 2009 –Revised July 2010

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