![](http://datasheet.mmic.net.cn/370000/PFR4200MAE40_datasheet_16728610/PFR4200MAE40_46.png)
Device Overview
MFR4200 Data Sheet, Rev. 0
46
Freescale Semiconductor
2.4
Modes of Operation
2.4.1
Overview
The MFR4200 device operates only in one user mode — the normal mode. In normal mode, different host
interfaces can be selected, each with its own associated external pin and interface configurations. The
device has no low power modes.
2.4.2
Recommended Pullup/down Resistor Values
As IF_SEL[0:1] and CLK_S[0:1] signals share pins with physical layer interface signals, pullup/down
devices must be used for selection. Recommended pullup/down resistor values for the IF_SEL[0:1] and
CLK_S[0:1] inputs are given in
Table 2-9
.
2.4.3
Host Controller Interfaces
The FlexRay communication controller can be connected to and controlled by microcontrollers with two
types of interface. The MCU type is selected by the IF_SEL0 and IF_SEL1 inputs as shown in
Section 2.1.3.1, “Interface Selection
”.
The CC latches the values of the IF_SEL0 and IF_SEL1 signals when it leaves the hard reset state. The
CC configures the interface for the type of MCU based on the latched values. The CC latches the values
again after it has left the hard reset state (see
Section 3.9.1, “Hard Reset State
”).
NOTE
If the CC senses an unsupported mode on its IF_SEL pins, it stops all
internal operations, does not perform or respond to any host transactions,
stays in configuration mode, and does not integrate into the communication
process. The following steps must be taken to select a correct MCU interface
mode:
1. IF_SEL0, IF_SEL1 must be set to AMI or to HCS12 mode;
2. The hard reset signal of the CC must be asserted again.
Table 2-9. Recommended Pullup/down Resistor Values for IF_SEL[0:1] and CLK_S[0:1] Inputs
IO, Regulator, and Analog Supply Level (
V
DD5
)
Pullup Resistor
1
1
The listed values are calculated for the MFR4200 physical layer connection where no internal pullup/down resistors are
assumed in the Electrical PHY at the TXD_BG1, BGT, ARM and MT interface lines. If an Electrical PHY device has internal
pullup/down resistors connected to those signals, then the external pullup/down resistor values must be recalculated to
ensure that V
IL
requirements for pulldown resistors or V
IH
requirements for pullup resistors for the chosen VDD5 are met.
Refer to
Section A.1.9, “I/O Characteristics
” for more information on VIL, VIH and VDD5.
Pulldown Resistor
1
Units
3.3V
16
47
kOhm
5V
10
47
kOhm