MPC555
/
MPC556
MODULAR INPUT/OUTPUT SUBSYSTEM (MIOS1)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
15-38
15.15 MIOS1 Function Examples
The versatility of the MIOS1 timer architecture is based on multiple counters and cap-
ture/compare channel units interconnected on 16-bit counter buses. This section in-
cludes some typical application examples to show how the submodules can be
interconnected to form timing functions. The diagrams used to illustrate these exam-
ples show only the blocks utilized for that function.
To illustrate the timing range of the MIOS1 in different applications, many of the follow-
ing paragraphs include time intervals quoted in microseconds and seconds. The as-
sumptions used are that f
SYS
is at 40 MHz with minimum overall prescaling (50 ns
cycle) and with the maximum overall prescaling (32 µs cycle). For other f
SYS
clock cy-
cle rates and prescaler choices, the times mentioned in these paragraphs scale appro-
priately.
15.15.1 MIOS1 Input Double Edge Pulse Width Measurement
To measure the width of an input pulse, the MIOS double action submodule (MDASM)
has two capture registers so that only one interrupt is needed after the second edge.
The software can read both edge samples and subtract them to get the pulse width.
The leading edge sample is double latched so that the software has the time of one
full period of the input signal to read the samples to be sure that nothing is lost. De-
pending on the prescaler divide ratio, pulse width from 50 ns to 6.7 s can be mea-
sured. Note that a software option is provided to also generate an interrupt after the
first edge.
MIOS1RPR1
— MIRSM1 Request Pending Register
0x30 6C46
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
IRP31 IRP30 IRP29 IRP28 IRP27
RESERVED
IRP22
RESERVED
IRP19 IRP18 IRP17 IRP16
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Table 15-35 MIOS1RPR1 Bit Descriptions
Bit(s)
Name
Description
0
IRP31
MDASM31 IRQ pending bit
1
IRP30
MDASM30 IRQ pending bit
2
IRP29
MDASM29 IRQ pending bit
3
IRP28
MDASM28 IRQ pending bit
4
IRP27
MDASM27 IRQ pending bit
5:8
—
Reserved
9
IRP22
MMCSM22 IRQ pending bit
10:11
—
Reserved
12
IRP19
MPWMSM19 IRQ pending bit
13
IRP18
MPWMSM18 IRQ pending bit
14
IRP17
MPWMSM17 IRQ pending bit
15
IRP16
MPWMSM16 IRQ pending bit
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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