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SDMA Channels
MC68360 USER’S MANUAL
Figure 7-18. SDMA Bus Arbitration (Normal Operation)
The relative priority between the two IDMAs and the SDMA channels is user programmable.
Regardless of system configuration, if the IDMA is a bus master when a higher priority
SDMA channel needs to transfer over the bus, the SDMA will steal cycles from the IDMA
with no arbitration overhead.
When the QUICC is in slave mode (CPU32+ is disabled) the SDMA can steal cycles from
the IDMA with no arbitration overhead. See Section 4 Bus Operation for diagrams of bus
arbitration by an internal master in slave mode.
7.7.2 SDMA Registers
The SDMA channels have one configuration register; otherwise, they are controlled trans-
parently to the user, through the configuration of the SCCs, SMCs, and SPI. The only user-
accessible registers associated with the SDMA are the SDMA configuration register
(SDCR), SDMA address register (SDAR), a read-only register used for diagnostics in case
of an SDMA bus error, and the SDMA status register (SDSR).
7.7.2.1 SDMA CONFIGURATION REGISTER (SDCR). The 16-bit SDCR is used to config-
ure all 14 SDMA channels. It is always readable and writable in the supervisor mode,
although writing the SDCR is not recommended unless the CP is disabled. SDCR is cleared
at reset.
AS
(OUTPUT)
DSACKx
(I/O)
S0
S2
S4
S0
S2
S4
S0
S2
S4
S0
OTHER CYCLE
NOTES:
1. The BCLRO signal is only asserted if the SDMA bus arbitration ID is greater than
the BCLROID2–BCLROID0 bits in the SIM60 module configuration register.
2. The BR, BG, and BGACK signals are not affected by the SDMA bus arbitration
process if the CPU32+ is enabled.
CLKO1
SDMA READ
(32 BITS)
BCLRO
(OUTPUT)
BR
(INPUT)
BG
(OUTPUT)
BGACK
(I/O)
SDMA INTERNALLY
REQUESTS BUS
NEGATED DURING
FINAL SDMA
BUS CYCLE
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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