MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
12-54
Freescale Semiconductor
shows an example of the termination signals protocol for back-to-back reads to two different
slave devices who properly take turns driving the termination signals. This assumes a system using slave
devices that drive termination signals.
Figure 12-37. Termination Signals Protocol Timing Diagram
12.4.2.10 Bus Operation in External Master Mode
External master mode enables an external master to access the internal address space of the MCU.
shows how to connect an MCU to an external master (a second MCU) and a shared SDR
memory to operate in external master mode. Multi-master support is only available in the MPC5554.
Limited support for external master accesses (master/slave systems only) is available in the MPC5553, see
Section 12.5.5, “Dual-MCU Operation with Reduced Pinout MCUs
1
Latched version (1 cycle delayed) used for externally driven
TEA and TA.
T
he EBI drives address and control signals an extra cycle because it uses a latched version of TA
*
Th
is is the earliest that the EBI can start another transfer, in the case of continuing a set of small accesses.
For all other cases, an extra cycle is needed before the EBI can start another TS.
**
CLKOUT
BB
TS
DATA[0:31]
TA, TEA
ADDR[8:31]
RD_WR
TSIZ[0:1]
Slave 1
Slave 2
*
*
**
(1 cycle delayed) to terminate the cycle. An external master is not required to do this.
Slave 1
negates
acknowledge
signals and
‘turns off’
Slave 2
negates
acknowledge
signals and
‘turns off’
Slave 2
allowed to
drive
acknowledge
signals
Slave 1
allowed to
drive
acknowledge
signals
Summary of Contents for MPC5553
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