AN2503 Freescale Semiconductor / Motorola, AN2503 Datasheet - Page 34

• Manufacturer Part Number: AN2503
• Description: Slave LIN Driver for the MC68HC908QT/QY Family
• Manufacturer: Freescale Semiconductor / Motorola

AN2503/D
34
1. CPU usage represents the time spent in the communication ISR(s) vs. time spent doing other tasks. API functions and
2. From LIN08 Driver User's Manual: CPU performance is calculated as: L = T active / T frame * 100%
3. For received data (command) messages, 0x55 data and checksum used for worst case ISR load.
4. EY16 CPU usage information was measured based on 4.9152 MHz CPU frequency, then recalculated for a 3.2 MHz CPU
handling performed outside of the ISR(s) is not counted against this metric. Average value is reported as a percentage of
times, but is still a function of CPU speed, as LIN communications is asynchronous to CPU operations. CPU usage
numbers are approximate. Peak time represents the longest single interrupt which that be processed.
where:
- L is the CPU load in percent;
- T active is the amount of CPU time expended in executing the driver code during T frame;
- T frame is the amount of time required to transmit or receive a regular LIN bus frame of maximum length, containing
8 bytes of data (124 bits). The required LIN message budget of 40% is also taken into account. For Reference: T frame
(9615 bps) = 18.055 ms; T frame (19230 bps) = 9.028 ms.
frequency.
QY/QT bit-banged
AN2503/D
QY/QT bit-banged
AN2599/D
EY16 ESCI
AN2575/D
LINQL4-ASM
AN2633/D
LINQL4-C
AN2633/D
LINQL4-API
AN2633/D
drivers
drivers
drivers
Version
Slave LIN Driver for the MC68HC908QT/QY Family
Freescale Semiconductor, Inc.
API
Std
N
Y
N
N
N
Y
For More Information On This Product,
Table 14. Driver Performance Metrics
(8-byte msg)
Msg Frame
Interrupts/
111 Rx
Go to: www.freescale.com
120 Tx
106 Tx
No. of
97 Rx
12
2
(3)
LIN Bus
19,230
19,230
19,230
19,230
19,230
19,230
Speed
9,615
9,615
9,615
9,615
9,615
9,615
CPU Speed
(calculated)
(MHz)
3.2
3.2
3.2
(4)
14% (rx)
20% (tx)
29% (rx)
40% (tx)
20% (rx)
20% (tx)
38% (rx)
44% (tx)
2% (rx)
4% (tx)
4% (rx)
7% (tx)
0.3 (rx)
0.2 (tx)
0.5 (rx)
0.5 (tx)
0.4 (rx)
0.4 (tx)
0.8 (rx)
0.8 (tx)
0.8 (rx)
0.8 (tx)
1.6 (rx)
1.7 (tx)
Average
(2)
CPU Usage
MOTOROLA
193 µs
272 µs
123 µs
39 µs
34 µs
61 µs
Peak
(1)