External Bus Interface (EBI)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
29-51
Preliminary
Figure 29-39. MCU Connected to Multiple Memories
29.5.5
Dual-MCU Operation with Reduced Pinout MCUs
Some MCUs with this EBI may not have all the pins described in this document pinned out for a particular
package. Some of the most common pins to be removed are AD[16:31], arbitration pins (BB, BG, BR),
and TSIZ[0:1]. This section describes how to configure dual-MCU systems for each of these scenarios.
More than one section may apply if the applicable pins are not present on one or both MCUs.
NOTE
The MPC5510 does not have TSIZ[0:1] or arbitration pins (BB, BR, BG).
29.5.5.1
Connecting 16-Bit MCU to 32-Bit MCU (Master/Master or Master/Slave)
This scenario is straightforward. Connect AD[0:15] between both MCUs, and configure both for 16-bit
data bus mode operation (DBM=1 in EBI_MCR). 32-bit external memories are not supported in this
scenario.
29.5.5.2
No Transfer Acknowledge (TA) Pin
If an MCU has no TA pin available, this restricts the MCU to chip-select accesses only. Non-chip-select
accesses have no way for the EBI to know which cycle to latch the data. The EBI has no built-in protection
CLKOUT
CS0
TS
WE0
ADDR[8:29]
DATA[0:31]
BDIP
OE
MCU
CK
CE
ADV
WE**
A[0:21]
D[0:31]
OE
BAA*
SDR
Memory
CK
CE
ADV
WE**
A[0:21]
D[0:31]
OE
BAA*
SDR
Memory
CS1
WE1
* May or may not be connected, depending on the memory used.
Flash memories typically use one WE signal as shown, RAMs use two or four (16-bit or 32-bit).
**