External Bus Interface (EBI)
MPC5644A Microcontroller Reference Manual, Rev. 6
284
Freescale Semiconductor
For chip-select accesses to a 16-bit port, only WE[0:1]/BE[0:1] are used by the EBI, regardless of which
half of the DATA bus is selected via the D16_31 bit in the EBI_MCR.
Section 14.5.1.10, Four Write/Byte Enable (WE/BE) Signals
for more details on WE[0:3]/BE[0:3]
functionality.
14.3.3
Signal output buffer enable logic by mode
describes how the EBI drives its output buffer enable (OBE) signals. These are internal signals
from the EBI to device logic outside the EBI, that determine when the EBI strongly drives values on pins.
When the OBE for an EBI signal is asserted (1), the EBI strongly drives the value on that pin. When the
OBE is negated (0), the EBI does not drive the signal, and the value is determined by internal or external
pullups/pulldowns, and/or device logic outside EBI block. The logic in
can be overwritten by
device logic, so see the device-specific documentation for any exceptions to the logic below.
14.4
Memory map/Register definition
shows the EBI registers.
Table 14-3. Signal Output Buffer Enable Logic by Mode
1
1
The values in this table only indicate when signals are strongly driven, not the logic value on the pin itself.
Signal
OBE Value by Mode (1=strongly driven, 0=not driven by EBI)
Module Disable Mode
2
(EXTM=X, MDIS=1)
2
This assumes that the clock to the EBI is shut off when MDIS=1. This is an optional device feature. If the clocks are
left running to EBI even when MDIS=1, then the EBI OBE behavior is as if in Single Master Mode (though EBI
accesses are not supported in this scenario).
Single Master Mode
(EXTM=0, MDIS=0)
ADDR[3:31]
0
1
BDIP
0
1
CAL_CS[0:3]
0
1
DATA[0:31]
0
Only 1 during write access or on Address
phase when Addr/Data muxing is enabled.
OE
0
1
RD_WR
0
1
TA
0
Only 1 during chip-select (or
cal-chip-select) SETA=0 access
TS
0
1
WE[0:3]/BE[0:3]
0
1
Table 14-4. EBI Address Map
Address
Use
EBI_BASE (0xC3F8_4000)
EBI Module Configuration Register (EBI_MCR)
E0x4
Reserved
Summary of Contents for MPC5644A
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