MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
307
Preliminary—Subject to Change Without Notice
For EBI-mastered accesses, the operation in 16-bit Data Bus Mode (DBM=1, PS=x) is similar to a
chip-select access to a 16-bit port in 32-bit Data Bus Mode (DBM=0, PS=1), except for the case of a
non-chip-select access of exactly 32-bit size.
External master accesses and EBI-mastered non-chip-select accesses of exactly 32-bit size are supported
via a two (16-bit) beat burst for both reads and writes. See
Section 13.5.2.11, “Non-Chip-Select Burst in
. Non-chip-select transfers of non-32-bit size are supported in standard non-burst
fashion.
16-bit Data Bus Mode is entered when DBM=1 in the EBI_MCR. Some MCUs may have DBM=1 by
default out of reset. See the device-specific Soc Guide for the DBM and D16_31 reset values.
13.2.3.7
Multiplexed Address on Data Bus Mode
This mode covers several cases aimed at reducing pin count on MCU and external components. In this
mode, the DATA pins will drive (for internal master cycles) the address value on the first clock of the cycle
(while TS is asserted). The DATA pins will also be used to sample the incoming address on the first clock
of a cycle for external master accesses.
An external master can connect to an internal master part in this mode, by setting the MCR[AD_MUX]
for both the internal master and the external master.
The memory controller supports per-chip-select selection of multiplexing address/data through the
BRx[AD_MUX] bit.
Address on Data bus multiplexing also supports the 16-bit data bus mode (MCR[DBM]=1) and 16-bit
memories (ORx[PS]=1). The user can select which 16 data signals are used (DATA[0:15] or
DATA[16:31]) by writing the D16_31 bit in the EBI_MCR. For either setting of D16_31, the 16 LSBs of
external address (ADDR[16:31]) are driven onto the selected 16 DATA pins. If additional address lines are
required to interface to the memory, then non-muxed address pins are sometimes (see note below) required
to complete the address space (e.g. ADDR[8:15] are commonly present as non-muxed address pins).
NOTE
To ease SoC integration, the EBI also drives the unused 16 DATA signals
with the MSBs of the external address, zero-padded in front (e.g. when
D16_31 bit is set for SoC with 24 ADDR pins, the EBI drives
(0b00000000,ADDR[8:15]) on DATA[0:15]. This allows an SoC to
optionally use DATA[8:15] for the upper 8 external address lines instead of
requiring separate non-muxed ADDR[8:15] pins. This is relevant primarily
for SoCs that support both 32-bit and 16-bit A/D muxed operation, so
therefore have DATA[0:31] pins present on the SoC, and in that case are not
required to have separate ADDR pins. See
.
For more details (e.g. timing diagrams), see
Section 13.5.2.14, “Address Data Multiplexing
13.2.3.8
Debug Mode
When the MCU is in Debug Mode, the EBI behavior is unaffected and remains dictated by the mode of
the EBI.
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