Texas Instruments TMS320C3x 사용자 설명서
Serial Ports
12-39
Peripherals
Figure 12–29. Exiting Fixed Continuous Mode Without Frame Sync, FSX Internal
CLKX
FSX
(internal)
DX
LOAD DXR
SET XFSM
RESET XFSM
A1
AN
B1
BN
C1
CN
D1
DN
E1
EN
F1
FN
1st word
2nd word
3rd word
4th word
5th word
12.2.12.2 Variable Data-Rate Timing Operation
The following variations are included in variable data-rate timing operations.
-
Variable Burst Mode
In burst mode with variable data-rate timing, FSX/FSR pulse lasts for the
entire duration of transfer. With an internally generated FSX (see
Figure 12–30), transmission is initiated by loading DXR. In this mode there
is a delay of approximately 3.5 CLKX cycles (depending on CLKX and H1
freqency) from the time DXR is loaded until FSX occurs. With an external
FSX, the FSX pulse initiates the transfer and the 3.5-cycle delay effectively
becomes a setup requirement for loading DXR with respect to FSX. There-
fore, in this case, you must load DXR no later than four CLKX cycles before
FSX occurs. Once the XSR is loaded from the DXR, an XINT is generated.
entire duration of transfer. With an internally generated FSX (see
Figure 12–30), transmission is initiated by loading DXR. In this mode there
is a delay of approximately 3.5 CLKX cycles (depending on CLKX and H1
freqency) from the time DXR is loaded until FSX occurs. With an external
FSX, the FSX pulse initiates the transfer and the 3.5-cycle delay effectively
becomes a setup requirement for loading DXR with respect to FSX. There-
fore, in this case, you must load DXR no later than four CLKX cycles before
FSX occurs. Once the XSR is loaded from the DXR, an XINT is generated.
Figure 12–30. Variable Burst Mode
DXR loaded
XINT
RINT
CLKX/R
FSR/FSX (external)
FSX (internal)
DX/DR
A1
AN
R/XVAREN = 1
R/XFSM = 0