Circuit Board Reference Manual

External Signals
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 17-3
Figure 17-2. Multiplexed FlexBus Implementation
17.4 External Signals
This section describes the external signals that are involved in data transfer operations. Table 17-1
summarizes the MCF548x FlexBus signals.
Table 17-1. FlexBus Signal Summary
Signal Name Direction Description Reset State
FBCS[5:0] O General purpose chip-selects Hi-Z
AD[31:0] I/O Address / Data bus Hi-Z
ALE O Address Latch Enable Hi-Z
BE
/BWE[3:0] O Byte Selects Hi-Z
OE O Output Enable Hi-Z
R/W O Read/Write. 1 = Read, 0 = Write Hi-Z
TBST O Burst Transfer indicator Hi-Z
TSIZ[1:0] O Transfer Size Hi-Z
TA I Transfer Acknowledge —
AD[31:0]
FlexBus
Interface
Controller
DATA[31:Y]
ADDR[X:0]
Address
Latch
Logic
External Device / Peripheral
ALE
R/W
TA
FBCSx
ALE
R/W
TA
CS
BE/BWE[3:0]
BE
/BWE[3:0]
OE
OE
SIZ[1:0]
TSIZ[1:0]
TBST
BURST