Texas Instruments TMS570LC4357

Pin CC6
L00-CNT-DF 20 21 22 23 24
L01-WCAP-DF 22
L02-WCAP-DF 21 24
LRP
R
QR
QR
OKRL
e1 e2
RL
OK
TU Delay Frame
r(n)
f(n)
f(n-1)
R
RL
e1 e2
RL
r(n+1)
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1142
SPNU563A–March 2018
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High-End Timer Transfer Unit (HTU) Module
The control fields of the HET instructions provide a 2-bit field to configure one of the following possibilities
(as shown in Table 24-2). A 3-bit field in the program field will select which of the 8 Double Control
Packets will be triggered by the request.
Table 24-2. Triggered Control Packets
Request Type Bit 1 Request Type Bit 0 Request Number
Don't care 0 No request
Specify number 0, 1,... or 7, which selects the
HTU or DMA request line.
0 1 Generate normal request
1 1 Generate quiet request
In the case of very light HTU load, but higher signal requirements (for example, high frequency), the quiet
request could also be used to define periods in which the data read by a control packet is safe. The
following HET code will capture counter time stamps to the L1-WCAP data field after rising edges (at pin
CC6) and to the L2-WCAP data field after falling edges (at pin CC6):
L0 CNT {reg=A, max=0x1FFFFFF}
L1 WCAP {reqnum=3, request=GENREQ, event=RISE, reg=A, pin=CC6}
L2 WCAP {reqnum=3, request=QUIET, event=FALL, reg=A, pin=CC7}
; HET HRSHARE feature configured to assign both WCAPs to pin CC6
Figure 24-12. Timing Example for Two WCAP Instructions
The HTU frame will have two elements: The first gives the time stamp of the rising edge r(n) and the
second gives the time stamp of the previous falling edge f(n-1). Using the code above, requests (R) and
the quiet requests (QR) will occur at the times shown in Figure 24-12, and a request lost will only be
signaled when the frame makes an access during the times marked with RL. So reading [22, 21] as frame
elements is correct. If the signal frequency would increase, then a wrong pair [22, 23] could be read, but
this will be signaled by a request lost error since at least e2 falls into the RL period.