ꢀ ꢁꢂ ꢃ ꢄ ꢅ ꢆꢇ ꢈ ꢉꢈ ꢀꢊ ꢀ ꢁꢂ ꢃ ꢄ ꢅ ꢆꢇ ꢈ ꢉꢋ ꢀꢊ ꢀ ꢁꢂ ꢃ ꢄꢅ ꢆꢇ ꢈꢉ ꢇꢀ
ꢌ ꢍꢎ ꢏꢐꢑꢒꢓ ꢍ ꢔꢀ ꢐꢍ ꢕꢍ ꢀꢖꢗ ꢂꢍ ꢕ ꢔꢖꢗ ꢒꢘ ꢓ ꢆꢏ ꢂ ꢂꢓ ꢘ ꢂ
SPRS226H − NOVEMBER 2003 − REVISED AUGUST 2005
MULTICHANNEL BUFFERED SERIAL PORT (McBSP) TIMING (CONTINUED)
†‡
timing requirements for McBSP as SPI Master or Slave: CLKSTP = 11b, CLKXP = 0 (see Figure 54)
−600, −720
−850, −1G
NO.
UNIT
MASTER
SLAVE
MIN MAX
MIN
12
4
MAX
4
5
t
t
Setup time, DR valid before CLKX high
Hold time, DR valid after CLKX high
2 − 12P
5 + 24P
ns
ns
su(DRV-CKXH)
h(CKXH-DRV)
†
‡
P = 1/CPU clock frequency in ns. For example, when running parts at 720 MHz, use P = 1.39 ns.
For all SPI Slave modes, CLKG is programmed as 1/4 of the CPU clock by setting CLKSM = CLKGDV = 1.
switching characteristics over recommended operating conditions for McBSP as SPI Master or
†‡
Slave: CLKSTP = 11b, CLKXP = 0 (see Figure 54)
−600, −720
−850, −1G
NO.
PARAMETER
UNIT
§
MASTER
SLAVE
MIN
MIN MAX
MAX
¶
1
2
3
t
t
t
Hold time, FSX low after CLKX low
L − 2 L + 3
T − 2 T + 3
ns
ns
ns
h(CKXL-FXL)
d(FXL-CKXH)
d(CKXL-DXV)
#
Delay time, FSX low to CLKX high
Delay time, CLKX low to DX valid
−2
4
12P + 2.8 20P + 17
12P + 3 20P + 17
8P + 2 16P + 17
Disable time, DX high impedance following last data bit from
CLKX low
6
t
−2
4
ns
ns
dis(CKXL-DXHZ)
7
t
Delay time, FSX low to DX valid
H − 2 H + 4
d(FXL-DXV)
†
‡
§
P = 1/CPU clock frequency in ns. For example, when running parts at 720 MHz, use P = 1.39 ns.
For all SPI Slave modes, CLKG is programmed as 1/4 of the CPU clock by setting CLKSM = CLKGDV = 1.
S = Sample rate generator input clock = 4P 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
7
FSX
DX
6
3
Bit 0
Bit(n-1)
Bit(n-1)
(n-2)
(n-3)
(n-3)
(n-4)
4
5
DR
Bit 0
(n-2)
(n-4)
Figure 54. McBSP Timing as SPI Master or Slave: CLKSTP = 11b, CLKXP = 0
123
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TI [ TEXAS INSTRUMENTS ]
