Electrical Specifications
†
Table 5−29. McBSP as SPI Master or Slave Timing Requirements (CLKSTP = 10b, CLKXP = 1)
MASTER
SLAVE
UNIT
MIN
12
4
MAX
MIN
MAX
‡
t
t
Setup time, BDR valid before BCLKX high
Hold time, BDR valid after BCLKX high
2 − 6P
ns
ns
su(BDRV-BCKXH)
‡
5 + 12P
h(BCKXH-BDRV)
†
‡
For all SPI slave modes, CLKG is programmed as 1/2 of the CPU clock by setting CLKSM = CLKGDV = 1.
P = 0.5 * processor clock
†
Table 5−30. McBSP as SPI Master or Slave Switching Characteristics (CLKSTP = 10b, CLKXP = 1)
§
MASTER
SLAVE
PARAMETER
UNIT
MIN
MAX
MIN
MAX
¶
t
t
t
Hold time, BFSX low after BCLKX high
T − 3 T + 4
D − 4 D + 3
ns
ns
ns
h(BCKXH-BFXL)
d(BFXL-BCKXL)
d(BCKXL-BDXV)
#
Delay time, BFSX low to BCLKX low
‡
‡
Delay time, BCLKX low to BDX valid
− 4
5
6P + 2
10P + 17
Disable time, BDX high impedance following last data bit from
BCLKX high
t
D − 2 D + 3
ns
dis(BCKXH-BDXHZ)
Disable time, BDX high impedance following last data bit from
BFSX high
‡
‡
‡
t
t
2P − 4
6P + 17
ns
ns
dis(BFXH-BDXHZ)
‡
Delay time, BFSX low to BDX valid
4P + 2
8P + 17
d(BFXL-BDXV)
†
‡
§
For all SPI slave modes, CLKG is programmed as 1/2 of the CPU clock by setting CLKSM = CLKGDV = 1.
P = 0.5 * processor clock
T
D
=
=
BCLKX period = (1 + CLKGDV) * 2P
BCLKX high pulse width = T/2 when CLKGDV is odd or zero and = (CLKGDV/2 + 1) * 2P 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).
#
LSB
MSB
BCLKX
BFSX
t
h(BCKXH-BFXL)
t
d(BFXL-BCKXL)
t
t
d(BFXL-BDXV)
dis(BFXH-BDXHZ)
t
t
t
d(BCKXL-BDXV)
dis(BCKXH-BDXHZ)
BDX
BDR
Bit 0
Bit(n-1)
(n-2)
(n-3)
(n-4)
t
su(BDRV-BCKXH)
h(BCKXH-BDRV)
(n-2)
Bit 0
Bit(n-1)
(n-3)
(n-4)
Figure 5−26. McBSP Timing as SPI Master or Slave: CLKSTP = 10b, CLKXP = 1
98
SPRS007D
November 2001 − Revised April 2004
TI [ TEXAS INSTRUMENTS ]
