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Data Sheet
43
Rev. 1.0, 2005-06-02
OctalLIU
TM
PEF 22508 E
Functional Description
The communication between the external micro controller and the OctalLIU
TM is done using a set of directly
accessible registers. The interface can be configured as Intel or Motorola type with a selectable data bus width of
8 or 16 bits.
The external micro controller transfers data to and from the OctalLIU
TM, sets the operating modes, controls
function sequences, and gets status information by writing or reading control and status registers. All accesses
can be done as byte or word accesses if enabled. If 16-bit bus width is selected, access to lower/upper part of the
data bus is determined by address line A0 and signal BHE / BLE as shown in Table 3 and Table 4.
Table 5 shows how the ALE (Address Latch Enable) line is used to control the bus structure and interface type.
The switching of ALE allows the OctalLIU
TM to be directly connected to a multiplexed address/data bus.
3.5.1.1
Mixed Byte/Word Access
Reading from or writing to the internal registers can be done using a 8-bit (byte) or 16-bit (word) access depending
on the selected bus interface mode. Randomly mixed byte/word access is allowed without any restrictions.
The assignment of registers with even/odd addresses to the data lines in case of 16-bit register access depends
on the selected asynchronous microprocessor interface mode:
Table 3
Data Bus Access (16-Bit Intel Mode)
BHE
A0
Register Access
OctalLIU
TM Data Pins Used
0
Register word access (even addresses)
D(15:0)
0
1
Register byte access (odd addresses)
D(15:8)
1
0
Register byte access (even addresses)
D(7:0)
1
No transfer performed
None
Table 4
Data Bus Access (16-Bit Motorola Mode)
BLE
A0
Register Access
OctalLIU
TM Data Pins Used
0
Register word access (even addresses)
D(15:0)
0
1
Register byte access (odd addresses)
D(7:0)
1
0
Register byte access (even addresses)
D(15:8)
1
No transfer performed
None
Table 5
Selectable asynchronous Bus and Microprocessor Interface Configuration
ALE
IM(1:0)
Asynchronous Microprocessor Interface Mode Bus Structure
Constant
level
01
Motorola
De-multiplexed
00
Intel
De-multiplexed
Switching
00
Intel
Multiplexed