- Texas Instruments Floating Point Digital Signal Processor Specification Sheet

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   
SPRS292 − OCTOBER 2005
98
POST OFFICE BOX 1443 • HOUSTON, TEXAS 77251−1443
switching characteristics over recommended operating conditions for McBSP as SPI master or
slave: CLKSTP = 10b, CLKXP = 1
†‡
(see Figure 50)
NO. PARAMETER
GDPA−167
ZDPA−167
−200
−250
UNIT
NO.
PARAMETER
MASTER
§
SLAVE
UNIT
MIN MAX MIN MAX
1 t
h(CKXH-FXL)
Hold time, FSX low
after CLKX high
¶
T − 2 T + 3 ns
2 t
d(FXL-CKXL)
Delay time, FSX low to CLKX low
#
H − 2 H + 3 ns
3 t
d(CKXL-DXV)
Delay time, CLKX low to DX valid −3 4 6P + 2 10P + 17 ns
6 t
dis(CKXH-DXHZ)
Disable time, DX high impedance following last data bit from
CLKX high
H − 2 H + 3 ns
7 t
dis(FXH-DXHZ)
Disable time, DX high impedance following last data bit from FSX
high
2P + 3 6P + 17 ns
8 t
d(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).
Bit 0 Bit(n-1) (n-2) (n-3) (n-4)
Bit 0 Bit(n-1) (n-2) (n-3) (n-4)
5
4
38
7
6
21
CLKX
FSX
DX
DR
Figure 50. McBSP Timing as SPI Master or Slave: CLKSTP = 10b, CLKXP = 1