Motorola DigitalDNA ColdFire MCF5272 User Manual page 190

Chip Select Registers
Table 8-5. CSORn Field Descriptions (Continued)
Name Name
9 RDAH Controls the address and attribute hold time after the termination, internal or external with TA,
of a read cycle that hits in the chip select address space.
0 Do not hold address and attribute signals an extra cycle after chip select negates on reads.
1 Hold address and attribute signals an extra cycle after chip select negate on reads.
8 EXTBURST Enable extended burst. Valid only for CS7. Reserved bit for CS[0:5]. EXTBURST should be 1
when external SDRAM is configured for a data bus narrower than the width programmed for
the MCF5272. EBI must be set for SDRAM and the BW must be set to the data bus width of
the external SDRAM array.
Example: If the MCF5272 external physical data bus width is 32 or 16 bits but the external
SDRAM is 16 bits wide, EXTBURST must be set and BW must be 10 (word) for SDCS.
0 Extended bursts are not enabled.
1 Extended bursts are enabled.
7 — Reserved, should be cleared.
6–2 WS Wait state generator. Specifies the number of wait states (in system clocks) needed before the
SIM generates an internal transfer acknowledge signal to terminate the access.
0x00 No wait states
0x01 1 wait state
...
0x1E 30 wait states
0x1F External access
For example, WS = 0x0A introduces a 10-clock wait before the bus cycle terminates; 0x1F
indicates a source external to the chip select module terminates the access.
For SRAM and ROM accesses EBI codes 00 or 11 and WS = 0x1F, TA must be driven from an
external source to terminate the bus cycle, otherwise the on-chip bus timeout monitor issues a
bus error exception.
For SRAM and ROM accesses with EBI = 00 or 11 and WS = 0x00–0x1E, the chip select
module terminates the bus cycle after the programmed number of system clocks.
For SDRAM accesses with SDCS, EBI = 01, and WS = 0x1F, bus cycles are terminated under
control of the SDRAM controller.
The CSOR0[WS] reset default is 0x1E. The default for all other CSORs is 0x00.
Caution: Never drive TA as an input to terminate SDRAM peripheral accesses.
1 RW RW and MRW determine whether the selected memory region is read only or write only.
0 Read only
1 Write only
0 MRW MRW must be set for value of RW be taken into consideration.
0 Memory covered by chip select is read/write. The memory covered by the chip select is
neither read nor write protected.
1 RW determines whether memory covered by chip select is read only or write only. A conflict
causes either a read or write protect violation.
8-6
Description
MCF5272 User's Manual