External Bus Interface
MPC885 PowerQUICC Family Reference Manual, Rev. 2
13-38
Freescale Semiconductor
13.4.10.1 RETRY
When an external device asserts RETRY during a bus cycle, the MPC885 enters a sequence in which it
terminates the current transaction, relinquishes bus ownership, and retries the cycle using the same
address, address attributes, and data (in the case of a write cycle).
Figure 13-29
shows that when the
internal arbiter is enabled, the MPC885 negates BB and asserts BG in the clock cycle after RETRY is
detected to allow any external master to gain bus ownership. Normal arbitration resumes in the next clock
cycle. If the external master does not use the bus, the MPC885 initiates a new transfer with the same
address and attributes as before.
Figure 13-29. Retry Transfer Timing–Internal Arbiter
CLKOUT
BR
BG (Output)
BB
R/W
TSIZ[0:1]
BURST
TS
Data
TA
RETRY
Allow external master
to gain the bus
A
A
A[0:31]
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...