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MPC8309CVMAGDCA 用户编程技术手册 - NXP（恩智浦）
制造商:
NXP（恩智浦）
分类:
微处理器
封装:
BGA-489
描述:
NXP MPC8309CVMAGDCA 芯片, 微处理器, 32位, 400MHZ, MAPBGA-489
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MPC8309CVMAGDCA数据手册
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PROFIBUS on the QUICC Engine Block, Rev. 1
6 Freescale Semiconductor
Using multiple peripherals in PROFIBUS mode
2 Using multiple peripherals in PROFIBUS mode
The following can preclude the usage of other QUICC Engine peripherals when the PROFIBUS mode of
operation is enabled:
• PROFIBUS nodes that respond to send/request frames are required to respond deterministically
• Dual port performance
The QUICC Engine block processes requests from enabled peripherals in round-robin style. If the user
enables another QUICC Engine peripheral, such as a UCC Ethernet controller, this peripheral may be
serviced directly before the timer for sending a response expires. This may lead to excessive response jitter,
especially at the higher baud rates (> 1.5 M). Enabling two UARTs in PROFIBUS mode may lead to
performance issues at the higher baud rates. This is more prevalent on devices that have a relatively low
QUICC Engine frequency.
For example, the MPC8306, as seen in Table 2, requires a QUICC Engine block running at 192 MHz. This
is approximately one instruction executed every 5 ns. At 12 Mbaud each bit is received 83 ns apart. The
QUICC Engine UART generates a request for every UART character. For PROFIBUS, each 8 bits of data
translates into 11 bits on the physical interface. Resultantly, the UART generates a request every 830 ns on
the UCC receiver. This yields 166 (830 ns/5 ns) clocks/instructions. However, the transmitter also needs
to be serviced. Assuming that the transmitter takes half the allotted cycles, this is 83 clocks for UCC Rx
and 83 clocks for the UCC Tx. Adding another port yields approximately 42 clocks per port, which can
lead to performance issues, increased latencies, and increased jitter.
This table provides device recommendations based on the protocols used and interface recommendations.
Table 5. Device recommendations
Number of
PROFIBUS
ports
PROFIBUS
baud rate
Fast Ethernet
Other QUICC
Engine
peripheral(s)
Recommendation
1 12 Mbaud No No Use any device.
1 > 6 Mbaud Yes No Use a device with a hardware Ethernet block, for
example a P10xx or LS10xx device.
1 ≤ 6 Mbaud Yes No Contact your local Freescale representative for
assessment of the performance and feasibility of your
requirements.
1 up to 12 Mbaud No Yes Contact your local Freescale representative for
assessment of the performance and feasibility of your
requirements.
1 ≤ 6 Mbaud Yes Yes Use a device with a hardware Ethernet block, for
example a P10xx or LS10xx device. Contact your
local Freescale representative for assessment of the
performance and feasibility of your QUICC Engine
requirements.
1 > 6 Mbaud Yes Yes Use a device with a hardware Ethernet block, for
example a P10xx or LS10xx device. Contact your
local Freescale representative for assessment of the
performance and feasibility of your QUICC Engine
requirements.
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