Motorola TMS320C6711D warranty MASTER§ Slave MIN, Clkx FSX, Bit Bitn-1

SPRS292 − OCTOBER 2005

MULTICHANNEL BUFFERED SERIAL PORT TIMING (CONTINUED)

switching characteristics over recommended operating conditions for McBSP as SPI master or slave: CLKSTP = 10b, CLKXP = 0†‡ (see Figure 48)

				GDPA−167
				ZDPA−167
NO.		PARAMETER			−200		UNIT
					−250
			MASTER§		SLAVE
			MIN	MAX	MIN	MAX
1	th(CKXL-FXL)	Hold time, FSX low	T − 2	T + 3			ns
		after CLKX low¶
2	td(FXL-CKXH)	Delay time, FSX low to CLKX high#	L − 2	L + 3			ns
3	td(CKXH-DXV)	Delay time, CLKX high to DX valid	−3	4	6P + 2	10P + 17	ns
6	tdis(CKXL-DXHZ)	Disable time, DX high impedance following last data bit from	L − 2	L + 3			ns
		CLKX low
7	tdis(FXH-DXHZ)	Disable time, DX high impedance following last data bit from			2P + 3	6P + 17	ns
		FSX high
8	td(FXL-DXV)	Delay time, FSX low to DX valid			4P + 2	8P + 17	ns

†P = 1/CPU clock frequency in ns. For example, when running parts at 250 MHz, use P = 4 ns.

‡For all SPI slave modes, CLKG is programmed as 1/2 of the CPU clock by setting CLKSM = CLKGDV = 1. § S = Sample rate generator input clock = 2P if CLKSM = 1 (P = 1/CPU clock frequency)

=Sample rate generator input clock = P_clks if CLKSM = 0 (P_clks = CLKS period)

T =	CLKX period = (1 + CLKGDV) * S
H =	CLKX high pulse width	= (CLKGDV/2 + 1) * S if CLKGDV is even
		= (CLKGDV + 1)/2 * S if CLKGDV is odd or zero
L =	CLKX low pulse width	= (CLKGDV/2) * S if CLKGDV is even

=(CLKGDV + 1)/2 * S if CLKGDV is odd or zero

¶FSRP = FSXP = 1. As a SPI master, FSX is inverted to provide active-low slave-enable output. As a slave, the active-low signal input on FSX and FSR is inverted before being used internally.

CLKXM = FSXM = 1, CLKRM = FSRM = 0 for master McBSP CLKXM = CLKRM = FSXM = FSRM = 0 for slave McBSP

#FSX should be low before the rising edge of clock to enable slave devices and then begin a SPI transfer at the rising edge of the master clock (CLKX).

CLKX
	1	2
FSX
	7	8
	6		3
DX	Bit 0	Bit(n-1)	(n-2)	(n-3)	(n-4)
		4	5
DR	Bit 0	Bit(n-1)	(n-2)	(n-3)	(n-4)

Figure 48. McBSP Timing as SPI Master or Slave: CLKSTP = 10b, CLKXP = 0

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