
SMJ320C6701
FLOATINGPOINT DIGITAL SIGNAL PROCESSOR
SGUS060 DECEMBER 2007
58
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
POST OFFICE BOX 1443
HOUSTON, TEXAS 772511443
MULTICHANNEL BUFFERED SERIAL PORT TIMING (CONTINUED)
switching characteristics for McBSP as SPI master or slave: CLKSTP = 11b, CLKXP = 1
(see Figure 36)
NO.
PARAMETER
’C6701-14
’C6701-16
UNIT
NO.
PARAMETER
MASTER§
SLAVE
UNIT
MIN
MAX
MIN
MAX
1
th(CKXH-FXL)
Hold time, FSX low after CLKX high
H 4
H + 4
ns
2
td(FXL-CKXL)
Delay time, FSX low to CLKX low#
T 4
T + 4
ns
3
td(CKXH-DXV)
Delay time, CLKX high to DX valid
4
3P + 1
5P + 17
ns
6
tdis(CKXH-DXHZ)
Disable time, DX high impedance following last data bit from
CLKX high
*2
*4
*3P + 4
*5P + 17
ns
7
td(FXL-DXV)
Delay time, FSX low to DX valid
*L 2
*L + 3
2P + 1
4P + 13
ns
*This parameter is not tested.
The effects of internal clock jitter are included at test. There is no need to adjust timing numbers for internal clock jitter. P = 1/CPU clock frequency
in ns. For example, when running parts at 167 MHz, use P = 6 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 = P 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).
Bit 0
Bit(n-1)
(n-2)
(n-3)
(n-4)
Bit 0
Bit(n-1)
(n-2)
(n-3)
(n-4)
5
4
3
7
6
2
1
CLKX
FSX
DX
DR
Figure 36. McBSP Timing as SPI Master or Slave: CLKSTP = 11b, CLKXP = 1