MCF5282CVM66 Datasheet, PDF (226/766 Pages) Freescale Semiconductor, Inc – MCF5282 and MCF5216 ColdFire® Microcontroller User’s Manual

External Interface Module (EIM)
13.3 Bus Characteristics
The device uses its system clock to generate CLKOUT. Therefore, the external bus operates at the same
speed as the bus clock rate, where all bus operations are synchronous to the rising edge of CLKOUT, and
some of the bus control signals (BS, OE, and CSn,) are synchronous to the falling edge, shown in
Figure 13-1. Bus characteristics may differ somewhat for interfacing with external DRAM.
CLKOUT
t_vo
t_ho
Rising-Edge
Signals
t_vo
t_ho
Falling-Edge
Signals
t_si
t_hi
Inputs
t_vo = Propagation delay of signal relative to CLKOUT edge
t_ho = Output hold time relative to CLKOUT edge
t_si = Required input setup time relative to CLKOUT edge
t_hi = Required input hold time relative to CLKOUT edge
Figure 13-1. Signal Relationship to CLKOUT for Non-DRAM Access
13.4 Data Transfer Operation
Data transfers between the processor and other devices involve the following signals:
• Address bus (A[23:0])
• Data bus (D[31:0])
• Control signals (TS and TA)
• CSn, OE, BS
• Attribute signals (R/W, SIZ, and TIP)
The address bus, write data, TS, and all attribute signals change on the rising edge of CLKOUT. Read data
is latched into the processor on the rising edge of CLKOUT.
The bus supports byte, word, and longword operand transfers and allows accesses to 8-, 16-, and 32-bit
data ports. Aspects of the transfer, such as the port size, the number of wait states for the external slave
being accessed, and whether internal transfer termination is enabled, can be programmed in the chip-select
control registers (CSCRs) and the DRAM control registers (DACRs).
Figure 13-2 shows the byte lanes that external memory should be connected to and the sequential transfers
if a longword is transferred for three port sizes. For example, an 8-bit memory should be connected to
D[31:24] (BS3). A longword transfer takes four transfers on D[31:24], starting with the MSB and going
to the LSB.
13-2
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Freescale Semiconductor