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Chip Select Module
MCF5272 ColdFire Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
8-3
8.2.1
Chip Select Base Registers (CSBR0–CSBR7)
The CSBRs,
Figure 8-1, provide a model internal bus cycle against which to match actual bus cycles to
determine whether a specific chip select should assert. A bus cycle in a specific chip select register causes
the assertion of the corresponding external chip select.
31
12 11
10
9
8
7
6
5
4
2
1
0
Field
BA
EBI
BW
SUPER
TT
TM
CTM ENABLE
Reset
CSBR0: 0x0000_0x011; CSBR1: 0x0000_1300; CSBR2: 0x0000_2300; CSBR3: 0x0000_3300;
CSBR4: 0x0000_4300; CSBR5: 0x0000_5300; CSBR6: 0x0000_6300; CSBR7: 0x0000_7700
R/W
Addr
0x040 (CSBR0); 0x048 (CSBR1); 0x050 (CSBR2); 0x058 (CSBR3);
0x060 (CSBR4); 0x068 (CSBR5); 0x070 (CSBR6); 0x078 (CSBR7)
Figure 8-1. Chip Select Base Registers (CSBRn)
Table 8-2. CSBRn Field Descriptions
Bits
Name
Description
31–12
BA
Base address. The starting address of the memory space covered by the chip select. BA is compared with
bits 31–12 of the access to determine whether the current bus cycle is intended for this chip select. Any
combination of BA bits can be masked in the associated CSOR.
11–10
EBI
External bus interface modes. These modes are used to multiplex outputs and determine timing of the
appropriate bus interface module onto the device pins.
00 16-/32-bit SRAM/ROM. For 16-/32-bit wide memory devices with byte strobe inputs. CSBR0[EBI] = 00
at reset. Affects all chip selects.
01 SDRAM. One physical bank of SDRAM consisting of 16–256 Mbit devices. CSOR7[WS] must be set
to 0x1F. Affects only CS7/SDCS.
10 Reserved
11 Use SRAM/ROM timing for 8-bit devices without byte strobe inputs.
9–8
BW
Bus width. Determines data bus size of the memory-mapped resource for all chip selects except CS0. It
is assumed that boot code for the processor is accessed through the global chip select CS0, so the initial
bus width for this chip select must be configured at reset. QSPI_CS0/BUSW0 and QSPI_CLK/BUSW1 are
used to program the bus width for CS0 at reset.
00 Longword (32 bits)
01 Byte (8 bits)
10 Word (16 bits)
11 Cache line (32 bits)
7
SUPER
Supervisor mode.
0 Bus cycle may be in user or supervisor mode (neglecting conditions imposed by setting CTM).
1 The chip select asserts a match only if the transfer modifier indicates a supervisor mode access. A user
access matching BA causes an access error.
SUPER, CTM, TT, and TM are used to restrict bus access. For example, if TT and TM indicate a user data
access and SUPER and CTM are both set, no accesses can occur.
6–5
TT
Transfer type. TT and TM may be used to further qualify the address match. If CTM is set, TT and TM must
match the access types for the chip select to assert. See the description of TM.