MC68MH360EM25L Freescale Semiconductor, MC68MH360EM25L Datasheet - Page 364

• Manufacturer Part Number: MC68MH360EM25L
• Description: IC MPU QUICC ETHER 25MHZ 240FQFP
• Manufacturer: Freescale Semiconductor

Specifications of MC68MH360EM25L

• Processor Type: M683xx 32-Bit
• Speed: 25MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 240-FQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -

IDMA Channels
interrupts, the IDMA may not be able to take its 128 clock allotment in a single burst. If, for
whatever reason, the IDMA is not able to take its full 128 clock allotment in a 1024 clock
cycle period, the IDMA is still only granted a 128 clock allotment in the next 1024 clock cycle
period.
7.6.4.4.3 External Burst Mode. For external devices requiring very high data transfer
rates, the external burst mode allows the IDMA to use all of the bus bandwidth to service the
device (see Figure 7-10). In the burst mode, the DREQx input to the IDMA is level-sensitive
and is sampled at falling edges of the clock to determine when a valid request is asserted
by the device. The device requests service by asserting DREQx and leaving it asserted. In
response, the IDMA begins to arbitrate for the system bus. If DREQx is negated prior to the
IDMA winning the bus, the IDMA will cease requesting the bus. If DREQx is negated long
enough for the IDMA to win the bus, cycles will continue as long as DREQx is asserted and
no higher priority bus master or interrupt occurs.
Each time the IDMA issues a bus cycle to either read or write the device, the IDMA will out-
put the DACKx signal. The device is either the source or destination of the transfers, as
7-40
(OUTPUT)
(OUTPUT)
(OUTPUT)
ECO = 1; PERIPHERAL IS READ.
NOTES:
ECO = 0; PERIPHERAL IS WRITTEN.
DSACKx
(INPUT)
DREQx
(INPUT)
DREQx
DACKx
CLKO1
DACKx
1. This example assumes dual address mode. In single address mode, the DREQx sample points would occur
2. This example assumes SRM = 1 in the CMR. If SRM = 0, DREQx would have to be asserted and negated one
(I/O)
S3 and S4) in all cycles shown above.
in every IDMA cycle.
clock earlier that what is shown to allow it to be internally synchronized by the IDMA before it is used.
Alternatively, the timing shown would be correct for the SRM = 0 case if a wait state were included (between
AS
S0
OTHER CYCLE
DREQ SAMPLED
LOW
DREQ SAMPLED
LOW
S2
S4
Freescale Semiconductor, Inc.
Figure 7-10. External Burst Requests;
For More Information On This Product,
S0
CONTINUE
BURST
IDMA READ
S2
MC68360 USER’S MANUAL
Go to: www.freescale.com
S4
CONTINUE
S0
BURST
IDMA WRITE
S2
S4
S0
IDMA READ
S2
STOP
BURST
S4
S0
IDMA WRITE
S2
STOP
BURST
S4
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