TMS320VC5470 datasheet(78/93 Pages) TI

78 / 93 page

Electrical Specifications

December 2001 – Revised December 2002

SPRS017B

High inactive state with delay; the McBSP transmits data one-half cycle ahead of the falling edge of BCLKX

and receives data on the falling edge of BCLKR.

Table 6–26 and Table 6–27 assume testing over recommended operating conditions, CLKSTP = 11b,

CLKXP = 1, and H = 0.5tc(CO) (see Figure 6–22).

NOTE: For all SPI slave modes, CLKG is programmed as 1/2 of the CPU clock by setting

CLKSM = CLKGDV = 1.

Table 6–26. McBSP as SPI Master or Slave Timing Requirements (CLKSTP = 11b and CLKXP = 1)

MASTER

SLAVE

UNIT

MIN

MAX

MIN

MAX

UNIT

tsu(BDRV-BCKXL)

Setup time, BDR valid before BCLKX low

– 12H

th(BCKXL-BDRV)

Hold time, BDR valid after BCLKX low

12H + 5

tsu(BFXL-BCKXL)

Setup time, BFSX low before BCLKX low

tc(BCKX)

Cycle time, BCLKX

12H

32H

Table 6–27. McBSP as SPI Master or Slave Switching Characteristics (CLKSTP = 11b and CLKXP = 1)

PARAMETER

MASTER†

SLAVE

UNIT

PARAMETER

MIN

MAX

MIN

MAX

UNIT

th(BCKXH-BFXL)

Hold time, BFSX low after BCLKX high‡

T – 6

T + 6

td(BFXL-BCKXL)

Delay time, BFSX low to BCLKX low§

C – 6

C + 6

td(BCKXH-BDXV)

Delay time, BCLKX high to BDX valid

– 3

6H + 5

10H + 14

tdis(BCKXH-BDXHZ)

Disable time, BDX high impedance following last data bit from

BCLKX high

– 2

6H + 3

10H + 17

td(BFXL-BDXV)

Delay time, BFSX low to BDX valid

C – 6

C + 6

4H – 2

8H + 17

† T = BCLKX period = (1 + CLKGDV) * 2H

C = BCLKX low pulse width = T/2 when CLKGDV is odd or zero and = (CLKGDV/2) * 2H when CLKGDV is even

D = BCLKX high pulse width = T/2 when CLKGDV is odd or zero and = (CLKGDV/2 + 1) * 2H when CLKGDV is even

‡ FSRP = FSXP = 1. As a SPI master, BFSX is inverted to provide active-low slave-enable output. As a slave, the active-low signal input on BFSX

and BFSR is inverted before being used internally.

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

CLKXM = CLKRM = FSXM = FSRM = 0 for slave McBSP

§ BFSX 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

(BCLKX).

Bit 0

Bit(n-1)

(n-2)

(n-3)

(n-4)

Bit 0

Bit(n-1)

(n-2)

(n-3)

(n-4)

BCLKX

BFSX

BDX

BDR

td(BFXL-BCKXL)

tsu(BDRV-BCKXL)

tdis(BCKXH-BDXHZ)

th(BCKXH-BFXL)

td(BCKXH-BDXV)

th(BCKXL-BDRV)

td(BFXL-BDXV)

LSB

MSB

tsu(BFXL-BCKXL)

tc(BCKX)

Figure 6–22. McBSP Timing as SPI Master or Slave: CLKSTP = 11b, CLKXP = 1

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