Programmable Clock and Framing
11-65
Multichannel Buffered Serial Ports
11.5.4 Clocking Examples
11.5.4.1 Double-Rate ST-BUS Clock
Figure 11–43 shows the McBSP timing to be compatible with the Mitel ST-
Bus
. The operation is running at maximum frame frequency.
-
CLK(R/X)M = 1: CLK(R/X)_int generated internally by sample rate generator
-
GSYNC = 1: CLKG is synchronized with the external frame sync signal in-
put on FSR. CLKG is not synchronized (it runs freely) until the frame sync
signal is active. Also, FSR is regenerated internally to form a minimum
pulse width.
-
CLKSM = 0: external clock (CLKS) drives the sample rate generator
-
CLKSP = 1: falling edge of CLKS generates CLKG and thus CLK(R/X)_int
-
CLKGDV = 1: receive clock (shown as CLKR) is half of CLKS frequency
-
FS(R/X)P = 1: active (low) frame sync pulse
-
(R/X)FRLEN1 = 11111b: 32 elements per frame
-
(R/X)WDLEN1 = 0: 8-bit element
-
(R/X)PHASE = 0: single-phase frame and thus (R/X)FRLEN2 =
(R/X)WDLEN2 = X
-
(R/X)DATDLY = 0: no data delay
Figure 11–43.
ST-BUS and MVIP Example
Sample point
E2B7
E1B0
E1B1
E1B2
E1B3
E1B4
E1B5
E1B6
E1B7
E2B7
E1B0
E1B1
E1B2
E1B3
E1B4
E1B5
E1B6
E1B7
E32B0
2.048-MHz CLKG,
CLKR_int,
CLKX_int (first FSR)
DR, DX
(subsequent FSR)
CLKG, CLKR_int,
CLKX_int
(subsequent FSR)
DR, DX (first FSR)
FSG, FSR_int,
FSX_int
FSR external
4.096-MHz CLKS