TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual
13-25
V2.0, 2007-07
EBU, V2.0
13.5
Master Mode Operation
In master mode, the EBU supports interconnection to a wide variety of
memory/peripheral devices with flexible programming of the access parameters. In the
following sections, the basic features for these access modes are described. The types
of external access cycles provided by the EBU are:
•
Asynchronous devices with demultiplexed access
– INTEL-style peripherals (separate RD and WR control signals)
– Motorola-style peripherals (MR/W signals)
– ROMs, EPROMs
– Static RAMs
•
Burst Mode Flash devices
Each TC1796 internal PLMB master can access external devices via the EBU. The EBU
provides four user-programmable external memory regions. Each of these regions is
provided with a set of registers that determine the parameters of the external bus
transaction and one chip select signal. A PLMB transaction that matches one of these
user-programmable external memory regions is translated by the EBU to the appropriate
external access(es).
In the TC1796, the EBU responds to the address ranges as defined in
.
The “compare” action means that the EBU compares the supplied PLMB address to all
its external regions. If a match is found, the EBU performs the appropriate external bus
access. Otherwise, the EBU generates a PLMB Error Acknowledge.
The “access registers” action means that the EBU is selected for a control/status register
access. The EBU performs the requested register access (or generates an PLMB Error
Acknowledge if there is no register at the supplied address).
For all address ranges that not listed in
the EBU is not selected and PLMB
requests are ignored.
Table 13-9
EBU External Address Ranges
Address Range
Description
Action
8080 0000
H
- 8FDF FFFF
H
External memory space (cached area)
compare
A080 0000
H
- AFDF FFFF
H
External memory space (non-cached area)
D800 0000
H
- DDFF FFFF
H
External Peripheral Space (non-cached area)
DE00 0000
H
- DEFF FFFF
H
External Emulator Space (non-cached area)
E000 0000
H
- E7FF FFFF
H
External Peripheral Space (non-cached area)
F800 0000
H
- F800 03FF
H
EBU Registers
access
register