PXN20RM Datasheet, PDF (850/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

Enhanced Modular Input/Output Subsystem (eMIOS200)
The input pulse period is calculated by subtracting the value in B1 from A2.
Figure 28-22 shows how the unified channel can be used for input period measurement.
EDPOL = 1
A
A
A
Input Signal¹
Selected
Counter Bus
0x000500
0x001000
0x001100
0x001250
0x001525
FLAG
Set Event
A2 (Captured)
Value²
B1 Value³
B2 (Captured)
Value
0xxxxxxx
0xxxxxxx
0xxxxxxx
0x001000
0xxxxxxx
0x001000
0x001250
0x001000
0x001250
A1 Value 0xxxxxxx
0xxxxxxx
0x001000
Notes: ¹ After input filter
2 _{EMIOS_CADR[n] = A2}
3 _{EMIOS_CBDR[n] = B1}
Figure 28-22. Input Period Measurement Example
0x0016A0
0x0016A0
0x001250
0x0016A0
0x001250
Figure 28-23 shows the A1 and B1 register updates when EMIOS_CADR[n] and EMIOS_CBDR[n] read
operations are performed. When EMIOS_CADR[n] read occurs, the content of A1 is transferred to B1 thus
providing coherent data in A2 and B1 registers. Transfers from B2 to B1 are then blocked until
EMIOS_CBDR[n] is read. After EMIOS_CBDR[n] is read, register A1 content is transferred to register
B1 and the transfers from B2 to B1 are re-enabled to occur at the transfer edges, which is the leading edge
in the Figure 28-23 example.
EDPOL = 1
A
Read EMIOS_CADR[n]
A
Read EMIOS_CBDR[n]
A
Input Signal¹
Selected
Counter Bus
FLAG
Set Event
A2 (Captured)
Value²
B2 (Captured)
Value
A1 Value
0x000500
0xxxxxxx
0xxxxxxx
0xxxxxxx
0x001000
0x001100
0x001000
0x001100
0x001250
0x001250
0x001250
0x001000
0x001525
0x001525
0x0016A0
0x0016A0
0x001250
B1 Value^{3 0xxxxxxx}
Notes: ¹ After input filter
2 _{EMIOS_CADR[n] = A2}
3 _{EMIOS_CBDR[n] = B1}
0x001000
0x001000
Figure 28-23. A1 and B1 Updates at EMIOS_CADR[n] and EMIOS_CBDR[n] Reads
0x001250
28-28
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor