
Bus Operation
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
20-22
Freescale Semiconductor
20.12.1 Master Reset
To perform a master reset, an external device asserts RSTI and DRESETEN simultaneously for a
minimum of six CLKIN cycles after VDD is within tolerance. This should always be done when power is
initially applied. A master reset resets the entire device including the SDRAM controller.
is a functional timing diagram of the master reset operation, illustrating relationships among
VDD, RSTI, DRESETEN, RSTO, mode selects, and bus signals.
CLKIN must be stable by the time VDD reaches the minimum operating specification. RSTI and
DRESETEN are internally synchronized on consecutive rising and falling clocks before being used. They
must meet the specified setup and hold times to the falling edge of CLKIN only if recognition by a specific
falling edge is required
.
Figure 20-21. Master Reset Timing
When the assertion of RSTI is recognized internally, the MCF5272 asserts the reset out pin (RSTO). The
RSTO pin is asserted as long as RSTI is asserted and remains asserted for 32,768 CLKIN cycles after RSTI
is negated.
During the master reset period, all outputs are driven to their default levels. Once RSTO negates, all bus
signals continue to remain in this state until the ColdFire core begins the first bus cycle for reset exception
processing.
The levels of the mode select inputs, QSPI_Dout/WSEL, QSPI_CLK/BUSW1, and QSPI_CS0/BUSW0,
are sampled when RSTO negates and they select the port size of CS0 and the physical data bus width after
a master reset occurs. The INTx signals are synchronized and are registered on the last falling edge of
CLKIN where RSTI is asserted.
A master reset causes any bus cycle (including SDRAM refresh cycles) to terminate. In addition, master
reset initializes registers appropriately for a reset exception. During an external master reset,
SCR[RSTSRC] is set to 0b11 to indicate that assertion of RSTI and DRESETEN caused the previous reset.
VDD
RSTI
Mode Select
CLKIN
RSTO
T >= 6
CLK CYCLES
T = 32,768
CLK CYCLES
T >= 22
CLK CYCLES
BUS SIGNALS
DRESETEN
Inputs
Содержание MCF5272 ColdFire
Страница 2: ......
Страница 38: ...MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 xxxviii Freescale Semiconductor...
Страница 60: ...MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 lx Freescale Semiconductor...
Страница 118: ...Local Memory MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 4 16 Freescale Semiconductor...
Страница 160: ...Debug Support MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 5 42 Freescale Semiconductor...
Страница 258: ...Ethernet Module MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 11 40 Freescale Semiconductor...
Страница 296: ...Universal Serial Bus USB MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 12 38 Freescale Semiconductor...
Страница 360: ...Timer Module MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 15 6 Freescale Semiconductor...
Страница 406: ...General Purpose I O Module MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 17 12 Freescale Semiconductor...
Страница 474: ...Bus Operation MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 20 26 Freescale Semiconductor...
Страница 528: ...List of Memory Maps MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 A 12 Freescale Semiconductor...
Страница 540: ...Index MCF5272 ColdFire Integrated Microprocessor User s Manual Rev 3 Index 10 Freescale Semiconductor...
Страница 543: ...blank...