Instruction Set
956
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
High-End Timer (N2HET) Module
20.6.3.21 SCNT (Step Count)
Syntax
SCNT {
[brk={OFF | ON}]
[next={label | 9-bit unsigned integer}]
step={8 | 16 | 32 | 64}
[control={OFF | ON}]
gapstart={25-bit unsigned integer}
[data={25-bit unsigned integer]
}
Figure 20-180. SCNT Program Field (P31:P0)
31
26 25
23
22
21
13 12
9
8
7
6
5
4
3
1
0
0
Reserved
BRK
Next program address
1010
Res.
00
Step
width
Res.
1
6
3
1
9
4
1
2
2
3
1
Figure 20-181. SCNT Control Field (C31:C0)
31
27
26
25
24
0
Reserved
Control
Res.
Gap start
5
1
1
25
Figure 20-182. SCNT Data Field (D31:D0)
31
7
6
0
Data
Reserved
25
7
Cycles
One or two cycles (two cycles when DF is involved in the calculations)
Register modified
Register A
Description
This instruction can be used only once in a program and defines a specialized
virtual timer used after APCNT and before ACNT to generate an angle-
referenced time base synchronized to an external signal (that is, a toothed
wheel signal) as defined in APCNT and ACNT. Step width selection bits are
saved in two flags, SWF0, and SWF1, to be re-used in ACNT.
SCNT multiplies the frequency of the external signal by a constant
K
defined
in the step width field, [P5:P4]. The bit encoding for this field is defined in
step
Specifies the step increment to be added to the counter value each
program resolution. These two bits provide the values for the SWF0
and SWF1 flags. The valid values are listed in
