MC68MH360RC25L Freescale Semiconductor, MC68MH360RC25L Datasheet - Page 144

• Manufacturer Part Number: MC68MH360RC25L
• Description: IC MPU QUICC 25MHZ 241-PGA
• Manufacturer: Freescale Semiconductor

Specifications of MC68MH360RC25L

• Processor Type: M683xx 32-Bit
• Speed: 25MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 241-PGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

Freescale Semiconductor, Inc.
C.3.1.1 Activation Procedure
If no S/T transceiver is active, no TCLK clock is generated. Once the first transceiver is
activated, it will generate a TCLK signal only if DCL and FSC signals are present as well.
Pseudo DCL and FSC signals generated from one of the baud rate generators (BRG) of the
QUICC32 can be used to generate the TCLK signal. The BRG can generate a clock based
on the QUICC32’s system clock. A divider factor should be chosen so that the BRG
frequency is close to 2.048 MHz. This clock then feeds into the 256-divider circuitry of
Figure C-4 to generate a pseudo DCL and a pseudo FSC.
A multiplexer commanded by the QUICC32 is required to select either the BRG signal or
the TCLK signals of the transceivers to be the clock master generating the DCL and FSC
signals.
When no transceiver is activated, the QUICC32 selects the BRG to be the clock master, and
the S/T interface receives the pseudo DCL and FSC signals. (These two signals are not
synchronized to the network but are not used to sample data.)
As the first MC145574 is activated, it will be able to generate the TCLK signal; see
Figure C-7. This transceiver will then send an interrupt to the QUICC32 (IRQ3—register
NR3[3]—meaning Info 2 has been received) indicating that the activation process has
begun. The QUICC32 then uses the multiplexer to select the TCLK signal of that
MC145574 to be the clock master.
As shown in Figure C-7 and Figure C-8, the TCLK signal is present before the interruption,
with at least 750 s between the IRQ and the received Info 4. The QUICC32 therefore has
750 s to react to the IRQ and to select the new clock master.
QMC Supplement
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