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Signal Descriptions
MC68360 USER’S MANUAL
2.1.2 Function Codes (FC3–FC0)
These three-state bidirectional signals identify the processor state and the address space
of the current bus cycle as noted in
Table 2-2. The function code pins provide the purpose
of each bus cycle to external logic.
Other bus masters besides the QUICC may also output function codes during their bus
cycles. On the QUICC, this capability is provided for each potential internal bus master (i.e.,
the IDMA, SDMA, and DRAM refresh units). Provision is also made for the decoding of func-
tion codes that are output from external bus masters (e.g., in the memory controller chip-
select generation logic).
In computer design, function code information can be used to protect certain portions of the
address map from unauthorized access or to extend the addressable range beyond the
address limit. However, in controller applications, function codes are most often used as a
debugging aid. Furthermore, in most controller applications, the QUICC stays continuously
in the supervisor state.
Refer to Section 4 Bus Operation for more information.
NOTE
FC3-0 may not be set to 0xF
2.1.3 Data Bus
The data bus consists of the following two groups. Refer to Section 4 Bus Operation for infor-
mation on the data bus and its relationship to bus operation.
2.1.3.1 DATA BUS (D31–D16). These three-state bidirectional signals (along with D15–
D0) provide the general-purpose data path between the QUICC and all other devices.
Although the data path is a maximum of 32 bits wide, it can be dynamically sized to support
8-, 16-, or 32-bit transfers. D31 is the MSB of the data bus. Byte and word operations occur
on D31–D16. Additionally, if the QUICC is configured into 16-bit bus mode, the D31–D16
Table 2-2. Address Space Encoding
Function Code Bits
3210
Address Space
0000
Reserved (Motorola)
0001
User Data Space
0010
User Program Space
0011
Reserved (User)
0100
Reserved (Motorola)
0101
Supervisor Data Space
0110
Supervisor Program Space
0111
Supervisor CPU Space
1
x
DMA Space
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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