T M S3 2 0 VC5 402
F I X ED ĆPOI N T DI G I TAL S I GN AL PRO CE SSO R
SPRS079E – OCTOBER 1998 – REVISED AUGUST 2000
multichannel buffered serial port timing (continued)
†
timing requirements for McBSP as SPI master or slave: [H=0.5t
(see Figure 34)
] CLKSTP = 11b, CLKXP = 1
c(CO)
MASTER
SLAVE
MIN MAX
UNIT
MIN
9
MAX
t
t
Setup time, BDR valid before BCLKX low
Hold time, BDR valid after BCLKX low
– 12H
ns
ns
su(BDRV-BCKXL)
0
5 + 12H
h(BCKXL-BDRV)
t
t
Setup time, BFSX low before BCLKX low
Cycle time, BCLKX
10
ns
ns
su(BFXL-BCKXL)
12H
32H
c(BCKX)
†
For all SPI slave modes, CLKG is programmed as 1/2 of the CPU clock by setting CLKSM = CLKGDV = 1.
switching characteristics for McBSP as SPI master or slave: [H=0.5t
CLKXP = 1 (see Figure 34)
] CLKSTP = 11b,
c(CO)
†‡
‡
MASTER
SLAVE
UNIT
PARAMETER
MIN MAX
MIN
MAX
§
t
t
t
Hold time, BFSX low after BCLKX high
D – 3 D + 4
T – 5 T + 3
ns
ns
ns
h(BCKXH-BFXL)
d(BFXL-BCKXL)
d(BCKXH-BDXV)
¶
Delay time, BFSX low to BCLKX low
Delay time, BCLKX high to BDX valid
–2
6
6H + 5 10H + 15
6H + 3 10H + 17
Disable time, BDX high impedance following last data bit from
BCLKX high
t
–2
4
ns
ns
dis(BCKXH-BDXHZ)
t
Delay time, BFSX low to BDX valid
C – 2 C + 4
4H – 2
8H + 17
d(BFXL-BDXV)
†
‡
For all SPI slave modes, CLKG is programmed as 1/2 of the CPU clock by setting CLKSM = CLKGDV = 1.
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).
¶
t
t
c(BCKX)
su(BFXL-BCKXL)
MSB
LSB
BCLKX
t
t
h(BCKXH-BFXL)
t
d(BFXL-BCKXL)
BFSX
t
t
d(BCKXH-BDXV)
(n-2)
dis(BCKXH-BDXHZ)
d(BFXL-BDXV)
BDX
Bit 0
Bit(n-1)
Bit(n-1)
(n-3)
(n-4)
t
su(BDRV-BCKXL)
t
h(BCKXL-BDRV)
BDR
Bit 0
(n-2)
(n-3)
(n-4)
Figure 34. McBSP Timing as SPI Master or Slave: CLKSTP = 11b, CLKXP = 1
60
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