MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
12-20
Freescale Semiconductor
12.4
Functional Description
12.4.1
External Bus Interface Features
12.4.1.1
32-Bit Address Bus with Transfer Size Indication
The transfer size for an external transaction is indicated by the TSIZ[0:1] signals during the clock where
address is valid. Valid transaction sizes are 8, 16, and 32 bits. In the MPC5554 and in the 416 BGA package
of the MPC5553, only 24 address lines are pinned out externally, but a full 32-bit decode is done internally
Table 12-11. EBI_ORn and EBI_CAL_ORn Field Descriptions
Bits
Name
Description
0–16
AM
[0:16]
Address mask. Allows masking of any corresponding bits in the associated base
register. Masking the address independently allows external devices of different size
address ranges to be used. Any clear bit masks the corresponding address bit. Any set
bit causes the corresponding address bit to be used in comparison with the address
pins. Address mask bits can be set or cleared in any order in the field, allowing a
resource to reside in more than one area of the address map. This field can be read or
written at any time.
Note: The upper 3 bits of the address mask (AM) field, EBI_ORx[0:2], are tied to a fixed
value of 111. These bits reset to their fixed value.
17–23
—
Reserved.
24–27
SCY
[0:3]
Cycle length in clocks. Represents the number of wait states (external bus cycles)
inserted after the address phase in the single cycle case, or in the first beat of a burst,
when the memory controller handles the external memory access. Values range from 0
to 15. This is the main parameter for determining the length of the cycle.
• The total cycle length for the first beat (including the TS cycle):
Section 12.5.3.1, “Example Wait State Calculation
28
—
Reserved.
29–30
BSCY
[0:1]
Burst beats length in clocks. This field determines the number of wait states (external
bus cycles) inserted in all burst beats except the first, when the memory controller starts
handling the external memory access and thus is using SCY[0:3] to determine the
length of the first beat.
• Total memory access length for each beat:
• Total cycle length (including the TS cycle):
Note: The number of beats (4, 8, 16) is determined by BL and PS bits in the base
register.
00 0-clock cycle wait states (1 clock per data beat)
01 1-clock cycle wait states (2 clocks per data beat)
10 2-clock cycle wait states (3 clocks per data beat)
11 3-clock cycle wait states (4 clocks per data beat)
(2 + SCY) external clock cycles
(1 + BSCY) External Clock Cycles
(2 + SCY) + [(Number of Beats – 1) x (BSCY + 1)]
Summary of Contents for MPC5553
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