![](http://datasheet.mmic.net.cn/370000/PFR4200MAE40_datasheet_16728610/PFR4200MAE40_38.png)
Device Overview
MFR4200 Data Sheet, Rev. 0
38
Freescale Semiconductor
2.2.3.7
WE#/RW_CC# — AMI Write Enable, HCS12 Read/Write Select
The function of this pin is selected by IF_SEL[0:1] pins. Refer to
Section 3.7, “Host Controller Interfaces
”
for more information. The pin can be configured to enable or disable either a pullup or pulldown resistor
on the pin.
WE# is an AMI interface write select signal. It strobes the valid data provided by the host on the D[15:0]
pins during write operations to the MFR4200 memory.
RW_CC# is an HCS12 interface read/write input signal. It indicates the direction of data transfer for a
transaction.
2.2.3.8
ECLK_CC — HCS12 Clock Input
ECLK_CC is the HCS12 interface clock input signal. The input clock frequency can be up to 8 MHz in
the HCS12 mode of the external interface block. The pin can be configured to enable or disable either a
pullup or pulldown resistor on the pin.
2.2.3.9
BGT/DBG2/IF_SEL0 — Bus Guardian Tick, Debug Strobe Point 2, Host
Interface Selection 0
BGT is a bus guardian tick clock output signal provided from the CC. If a Bus Guardian device is not used
in an application, this pin may be left open.
BGT is active, irrespective of which physical layer is selected. If the RS485 Driver type is selected, this
pin is not used.
This signal should be connected to the bus guardian on each channel. The pin can be configured to provide
either high or reduced output drive.
DBG2 is debug strobe point output 2. The function output on this pin is selected by the debug port control
register. Refer to
Section 3.10, “Debug Port
” for more information.
IF_SEL0 is the CC external interface selection input signal. Refer to
Table 2-1
for the selection coding.
NOTE
The IF_SEL[0:1] signals are inputs during the internal reset sequence and
are latched by the internal reset signal level.
While the IF_SEL0 value is being latched, the output drive control is
disabled and the internal pulldown resistor is connected to the pin.
As the IF_SEL[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] inputs are given in
Section 2.4.2, “Recommended Pullup/down Resistor Values
”.
2.2.3.10
MT/CLK_S1 — Bus Guardian Macrotick, Clock Output Select 1
MT is a Bus Guardian macrotick output signal from the CC. If a bus guardian device is not used in an
application, this pin may be left open.