Freescale Semiconductor MPC5565, Reference Manual

Page: 556 / 1153

SRAM
MPC5565 Microcontroller Reference Manual, Rev. 1.0
Freescale Semiconductor 14-3
3. The ECC is then calculated on the resulting 64 bits formed in the previous step.
4. The 8-bit ECC result is appended to the 64 bits from the data bus, and the 72-bit value is then
written to SRAM.
14.6.1 Access Timing
The system bus is a two-stage pipelined bus, which makes the timing of any access dependent on the access
during the previous clock.
Table 14-3 lists the various combinations of read and write operations to SRAM
and the number of wait states used for the each operation. The table columns contain the following
information:
Current operation Lists the type of SRAM operation executing currently
Previous operation Lists the valid types of SRAM operations that can precede the current SRAM
operation (valid operation during the preceding clock)
Wait states Lists the number of wait states (bus clocks) the operation requires which depends
on the combination of the current and previous operation
Table 14-3. Number of Wait States Required for SRAM Operations
Current Operation Previous Operation Number of Wait States Required
Read Operation
Read
Idle
1 Pipelined read
Burst read
64-bit write 2
8-, 16-, or 32-bit write
0
(read from the same address)
1
(read from a different address)
Pipelined read Read 0
Burst read
Idle
1,0,0,0 Pipelined read
Burst read
64-bit write 2,0,0,0
8-, 16-, or 32-bit write
0,0,0,0
(read from the same address)
1,0,0,0
(read from a different address)