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MPC180E Security Processor User’s Manual
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
EBI Controller Operation
Table 3-8 summarizes the operation in clock cycles of the EBI in MPC860 and MPC8260
modes.
Single accesses are those that are only to one address and for which one 32-bit data word
is transferred. For writes or reads to the execution units, it is possible that the EBI will
generate one or more wait states to the host. This is a function of the current programming
of the EBI registers and the state of the execution unit being addressed. At no time will the
EBI generate a wait state for an access to an EBI register (CSTAT, ID, IMASK, IBCTL,
IBCNT, OBCTL, OBCNT).
Burst accesses are defined as exactly four (MPC860 mode) or eight (MPC8260 mode)
32-bit writes or reads at consecutive addresses. A burst transfer begins by the assertion of
CS, TS, and BURST along with the address.
3.4.1 Buffer Accesses (FIFO Mode)
The controller contains an input buffer and an output buffer of 4096 bits each. These buffers
can be written to directly by the host or by using DMA. For direct access, the host simply
writes or reads the address of the buffer.
DREQ1 and DREQ2 (input/output buffer ready) are programmable handshake signals used
for buffer control. An external DMA controller can use this handshake to service the input
or output buffer with data transfers as required. The EBI CSTAT register determines
whether these signals reflect the state of the input buffer or output buffer. By default,
DREQ1 refers to the state of the input buffer and DREQ2 refers to the state of the output
buffer.
NOTE:
DREQx refers to either DREQ1 or DREQ2. Either can be
programmed to refer to the state of the input or output buffer.
In FIFO mode, the input buffer automatically fills and the output buffer automatically
empties. In the input buffer, this is accomplished by assertion of DREQx whenever at least
four 32-bit words (in MPC860 mode) or eight 32-bit words (in MPC8260 mode) of space
are available. Similarly, for the output buffer, DREQx remains asserted as long as at least
four 32-bit words (MPC860 mode) or eight 32-bit words (MPC8260 mode) are in the
output buffer to be read.
Table 3-8. EBI Operation Summary
Name
MPC860 Mode
CONFIG=0
MPC260 Mode
CONFIG=1
Single beat read/write to/from EBI register or FIFO
0
2
Single beat read/write to/from execution units
at least 2
at least 3
4-beat burst read/write to/from FIFOs
0
not supported
4-beat burst read/write to/from execution units
not supported
not supported
8-beat burst read/write to/from FIFOs
not supported
2
8-beat burst read/write to/from execution units
not supported
not supported
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Freescale Semiconductor, Inc.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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