Chapter 20. Bus Operation
20-5
Bus Characteristics
20.4 Bus Characteristics
The MCF5272 uses the address bus (A[22:0]) to specify the location for a data transfer and
the data bus (D[31:0] or D[31:16]) to transfer the data. Control signals indicate the direction
of the transfer. The selected device or the number of wait states programmed in the chip
select base registers (CSBRs), the chip select option registers (CSORs), the SDRAM
configuration and SDRAM timing registers (SDCR, SDTR) control the length of the cycle.
The MCF5272 clock is distributed internally to provide logic timing. All SRAM and ROM
mode bus signals should be considered as asynchronous with respect to CLKIN.
SDCR[INV] allows the SDRAM control signals to be asserted and negated synchronous
with the rising or falling edge of SDCLK. The SDRAM control signals are BS[3:0],
SDBA[1:0], RAS0, CAS0, SDWE, A10_PRECHG, SDCLKE, and CS7/SDCS.
The asynchronous INT[6:1] signals are internally synchronized to resolve the input to a
valid level before being used.
20.5 Data Transfer Mechanism
The MCF5272 supports byte, word, and longword operands and allows accesses to 8-, 16-,
and 32-bit data ports. The MCF5272 supports port sizes of the specific memory, enables
internal generation of transfer termination, and sets the number of wait states for the
external slave being accessed by programming the CSBRs, CSORs, SDCR, and SDTR. For
more information on programming these registers, refer to the SIM, chip select, and
SDRAM controller chapters.
NOTE:
The MCF5272 compares the address for the current bus
transfer with the address and mask bits in the CSBRs and
CSORs looking for a match. The priority is listed in Table 20-2
(from highest priority to lowest priority):
Table 20-2. Chip Select Memory Address Decoding Priority
Priority
Chip Select
Highest
Chip Select 0
Chip Select 1
Chip Select 2
Chip Select 3
Chip Select 4
Chip Select 5
Chip Select 6
Lowest
Chip Select 7
Summary of Contents for DigitalDNA ColdFire MCF5272
Page 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Page 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Page 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Page 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Page 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Page 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Page 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Page 338: ...13 44 MCF5272 User s Manual Application Examples ...
Page 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Page 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Page 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Page 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...