MC68EC040RC25 Freescale Semiconductor, MC68EC040RC25 Datasheet - Page 152

• Manufacturer Part Number: MC68EC040RC25
• Manufacturer: Freescale Semiconductor

Specifications of MC68EC040RC25

• Family Name: M68000
• Device Core: ColdFire
• Device Core Size: 32b
• Frequency (max): 25MHz
• Instruction Set Architecture: RISC
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Pin Count: 179
• Package Type: PGA
• Lead Free Status / Rohs Status: Supplier Unconfirmed

7.4.1 Byte, Word, and Long-Word Read Transfers
During a read transfer, the processor receives data from a memory or peripheral device.
Since the data read for a byte, word, or long-word access is not placed in either of the
internal caches by definition, the processor ignores the level on the transfer cache inhibit
(TCI) signal when latching the data. The bus controller performs byte, word, and long-word
read transfers for the following cases:
Figure 7-8 is a flowchart for byte, word, and long-word read transfers. Bus operations are
similar for each case and vary only with the size indicated and the portion of the data bus
used for the transfer. Figure 7-9 is a functional timing diagram for byte, word, and long-
word read transfers.
7-10
• Accesses to a disabled cache.
• Accesses to a memory page that is specified noncachable.
• Accesses that are implicitly noncachable (read-modify-write accesses and accesses
• Accesses that do not allocate in the data cache on a read miss (table searches,
• The first transfer of a line read is terminated with transfer burst inhibit (TBI), forcing
to an alternate logical address space via the MOVES instruction).
exception vector fetches, and exception stack deallocation for an RTE instruction).
completion of the line access using three additional long-word read transfers.
1) SET R/W TO READ
2) DRIVE ADDRESS ON A31–A0
3) DRIVE USER PAGE ATTRIBUTES ON UPA1, UPA0
4) DRIVE SIZE ON SIZ1, SIZ0 (BYTE, WORD,
5) DRIVE TRANSFER TYPE ON TT1, TT0
6) DRIVE TRANSFER MODIFIER ON TM2–TM0
7) CIOUT BECOMES VALID
8) ASSERT TS FOR ONE CLOCK
9) ASSERT TIP
1) LATCH DATA
OR LONG WORD)
Figure 7-8. Byte, Word, and Long-Word Read Transfer Flowchart
START NEXT CYCLE
ADDRESS DEVICE
ACQUIRE DATA
PROCESSOR
Freescale Semiconductor, Inc.
For More Information On This Product,
M68040 USER’S MANUAL
Go to: www.freescale.com
1) DECODE ADDRESS
2) PLACE DATA ON APPROPRIATE BYTES OF
3) ASSERT TA
1) REMOVE DATA FROM D31–D0
2) NEGATE TA
D31–D0 BASED ON SIZEx, A0, AND A1
EXTERNAL DEVICE
TERMINATE CYCLE
PRESENT DATA
MOTOROLA