XRT86L30
REV. 1.0.1
SINGLE T1/E1/J1 FRAMER/LIU COMBO
3.2
Motorola Mode Programmed I/O Access (Synchronous)
If the XRT86L30 is interfaced to a Motorola type µP, it should be configured to operate in the Motorola mode.
Motorola type programmed I/O Read and Write operations are described below.
Motorola Mode Read Cycle
Whenever a Motorola type µP wishes to read the contents of a register, it should do the following.
1. Place the address of the target register on the address bus input pins ADDR[11:0].
2. While the µP is placing this address value on the address bus, the address decoding circuitry should
assert the CS pin of the XRT86L30, by toggling it "Low". This action enables further communication
between the µP and the XRT86L30 microprocessor interface block.
3. The µP should then toggle the TS pin "Low". This step causes the XRT86L30 to latch the contents of the
address bus into its internal circuitry. At this point, the address of the register has now been selected.
4. Next, the µP should indicate that this current bus cycle is a Read operation by pulling the R/W input pin
"High".
5. Toggle the WE input pin "Low". This action enables the bi-directional data bus output drivers of the
XRT86L30.
6. After the µP toggles the WE signal "Low", the XRT86L30 will toggle the TA output pin "Low". The
XRT86L30 does this in order to inform the µP that the data is available to be read by the µP, and that it is
ready for the next command.
7. After the µP detects the TA signal and has read the data, it can terminate the Read Cycle by toggling the
WE input pin "High".
Motorola Mode Write Cycle
Whenever a motorola type µP wishes to write a byte or word of data into a register within the XRT86L30, it
should do the following.
1. Place the address of the target register on the address bus input pins ADDR[11:0].
2. While the µP is placing this address value on the address bus, the address decoding circuitry should
assert the CS pin of the XRT86L30, by toggling it "Low". This action enables further communication
between the µP and the XRT86L30 microprocessor interface block.
3. The µP should then toggle the TS pin "Low". This step causes the XRT86L30 to latch the contents of the
address bus into its internal circuitry. At this point, the address of the register has now been selected.
4. Next, the µP should indicate that this current bus cycle is a Write operation by pulling the R/W input pin
"Low".
5. Toggle the WE input pin "Low". This action enables the bi-directional data bus output drivers of the
XRT86L30.
6. After the µP toggles the WE signal "Low", the XRT86L30 will toggle the TA output pin "Low". The
XRT86L30 does this in order to inform the µP that the data has been written into the internal register loca-
tion, and that it is ready for the next command.
7. After the µP detects the TA signal and has read the data, it can terminate the Read Cycle by toggling the
WE input pin "High".
The Motorola Read and Write timing diagram is shown in Figure 4. The timing specifications are shown in
Table 7.
26
EXAR [ EXAR CORPORATION ]
