MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
331
Preliminary—Subject to Change Without Notice
Figure 13-8. Basic Transfer Protocol
The arbitration phase is where bus ownership is requested and granted. This phase is not needed in Single
Master Mode because the EBI is the permanent bus owner in this mode. Arbitration is discussed in detail
in
Section 13.5.2.8, “Arbitration
.
The address transfer phase specifies the address for the transaction and the transfer attributes that describe
the transaction. The signals related to the address transfer phase are TS, ADDR (or DATA if Address/Data
multiplexing is used), CS[0:3], RD_WR, TSIZ[0:1], and BDIP. The address and its related signals (with
the exception of TS, BDIP) are driven on the bus with the assertion of the TS signal, and kept valid until
the bus master receives TA asserted (the EBI holds them one cycle beyond TA for writes and external TA
accesses). Note that for writes with internal TA, RD_WR is not held one cycle past TA.
The data transfer phase performs the transfer of data, from master to slave (in write cycles) or from slave
to master (on read cycles), if any is to be transferred. The data phase may transfer a single beat of data (1-4
bytes) for non-burst operations or a 2-beat (special DBM=1 case only), 4-beat, 8-beat, or 16-beat burst of
data (2 or 4 bytes per beat depending on Port Size) when burst is enabled. On a write cycle, the master
must not drive write data until after the address transfer phase is complete. This is to avoid electrical
contentions when switching between drivers. The master must start driving write data one cycle after the
address transfer cycle. The master can stop driving the data bus as soon as it samples the TA line asserted
on the rising edge of CLKOUT. To facilitate asynchronous write support, the EBI keeps driving valid write
data on the data bus until 1 clock after the rising edge where RD_WR and WE are negated (for chip-select
accesses only). See
for an example of write timing. On a read cycle, the master accepts the
data bus contents as valid on the rising edge of the CLKOUT in which the TA signal is sampled asserted.
See
for an example of read timing.
The termination phase is where the cycle is terminated by the assertion of either TA (normal termination)
or TEA (termination with error). Termination is discussed in detail in
Section 13.5.2.9, “Termination
.
13.5.2.4
Single Beat Transfer
The flow and timing diagrams in this section assume that the EBI is configured in Single Master Mode.
Therefore, arbitration is not needed and is not shown in these diagrams. Refer to
Operation in External Master Mode
to see how the flow and timing diagrams change for External Master
Mode.
13.5.2.4.1
Single Beat Read Flow
The handshakes for a single beat read cycle are illustrated in the following flow and timing diagrams.
ARBITRATION
ADDRESS TRANSFER
DATA TRANSFER
TERMINATION