MSC8113 Reference Manual, Rev. 0
13-36
Freescale Semiconductor
System Bus
13.2.4 Data Tenure Operations
This section describes the operation of the MSC8113 device during the data bus arbitration,
transfer, and termination phases of the data tenure.
13.2.4.1 Data Bus Arbitration
The beginning of an address transfer, marked by the assertion of transfer start (
TS
), is also an
implicit data bus request if the transfer type signals (
TT[0–4]
) indicate that the transaction is not
address-only. (The address-only transactions are not applicable for MSC8113). The MSC8113
arbiter supports three external masters and uses
DBG
signals to grant the external master data bus.
The
DBG
signals are not asserted if the data bus, which is shared with memory, is busy with a
transaction. A qualified data bus grant occurs if
DBG
is asserted while the data bus operation
signals
DBB
and
ARTRY
are deasserted. The MSC8113 arbiter should assert
DBG
only when the
first
TA
is asserted with or after the associated
ARTRY
. The MSC8113
DBG
is asserted with
TS
if
the data bus is free and if PPC_ACR[DBGD] = 0. If PPC_ACR[DBGD] = 1 and the data bus is
not busy,
DBG
is asserted one cycle after
TS
. The
DBG
delay should ensure that
ARTRY
is not
asserted after the first or only
TA
assertion. For the programming model, see the discussion of the
60x Bus Arbiter Configuration Register (PPC_ACR) in Section 4.2.1, System Configuration and
Protection Registers.
Note:
DBB
should not be asserted after the data tenure is finished. Assertion of
DBB
after the
last
TA
causes improper operation of the bus. MSC8113 internal masters do not assert
DBB
after the last
TA
.
If the data bus is not busy with the data of a previous transaction on the bus, the external arbiter
must assert
DBG
in the same cycle in which
TS
is asserted (by a master that was granted the bus)
or in the following cycle. If the external arbiter asserts
DBG
on the cycle in which
TS
is asserted,
PPC_ACR[DBGD] should be set to zero. Otherwise, PPC_ACR[DBGD] should be set to one.
External masters connected to the system bus must assert
DBB
only for the duration of their data
tenure. External masters should not use
DBB
to prevent other masters from using the data bus after
their data tenure has ended.
13.2.4.2 Data Streaming Mode
A special MSC8113 data streaming mode improves bus performance in some conditions.
Generally, the bus protocol requires one idle cycle between any two data tenures to prevent
contention on the data bus when the driver of the data is changing. However, when the driver on
the data bus is the same for both data tenures, this idle cycle can be omitted. In data streaming
mode, the MSC8113 omits the idle cycle where possible. MSC8113 applications often require
data stream transfers of more than 4
×
64 bits. For example, the ATM cell payload is 6
×
64 (12
×
32) bits. All this data is driven from a single device on the bus, so data-streaming saves a cycle
for such a transfer. When data-streaming mode is enabled, transactions initiated by bus masters
within the device omit the idle cycle if the data driver is the same. Note that data streaming mode
Summary of Contents for MSC8113
Page 1: ...MSC8113 Reference Manual Tri Core 16 Bit Digital Signal Processor MSC8113RM Rev 0 May 2008 ...
Page 20: ...MSC8113 Reference Manual Rev 0 xx Freescale Semiconductor Contents ...
Page 28: ...MSC8113 Reference Manual Rev 0 xxviii Freescale Semiconductor ...
Page 56: ...MSC8113 Reference Manual Rev 0 1 28 Freescale Semiconductor MSC8113 Overview ...
Page 76: ...MSC8113 Reference Manual Rev 0 2 20 Freescale Semiconductor SC140 Core Overview ...
Page 134: ...MSC8113 Reference Manual Rev 0 4 30 Freescale Semiconductor System Interface Unit SIU ...
Page 168: ...MSC8113 Reference Manual Rev 0 6 18 Freescale Semiconductor Boot Program ...
Page 180: ...MSC8113 Reference Manual Rev 0 7 12 Freescale Semiconductor Clocks ...
Page 260: ...MSC8113 Reference Manual Rev 0 8 80 Freescale Semiconductor Memory Map ...
Page 300: ...MSC8113 Reference Manual Rev 0 9 40 Freescale Semiconductor Extended Core ...
Page 304: ...MSC8113 Reference Manual Rev 0 10 4 Freescale Semiconductor MQBus and M2 Memory ...
Page 308: ...MSC8113 Reference Manual Rev 0 11 4 Freescale Semiconductor SQBus ...
Page 590: ...MSC8113 Reference Manual Rev 0 17 46 Freescale Semiconductor Interrupt Processing ...
Page 614: ...MSC8113 Reference Manual Rev 0 18 24 Freescale Semiconductor Debugging ...
Page 622: ...MSC8113 Reference Manual Rev 0 19 8 Freescale Semiconductor Internal Peripheral Bus IPBus ...
Page 724: ...MSC8113 Reference Manual Rev 0 21 32 Freescale Semiconductor UART ...
Page 920: ...MSC8113 Reference Manual Rev 0 25 150 Freescale Semiconductor Ethernet Controller ...
Page 1171: ...MSC8113 Reference Manual Rev 0 Freescale Semiconductor C 61 EF wait_rts P 01077FFC 9F rts 71 ...
Page 1172: ...MSC8113 Reference Manual Rev 0 C 62 Freescale Semiconductor MSC8113 Boot Code ...
Page 1202: ...MSC8113 Reference Manual Rev 0 Index 30 Freescale Semiconductor Index ...