External Bus Interface
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
9-17
Refer to
Section 2.4, “Pad Module Configuration Register (PDMCR2)
Controller Option Registers (OR0–OR3)
,” for more information on PREDIS_EN, and EHTR
configuration bits.
Figure 9-11. Read Followed by Write when Pre-Discharge Mode is Enabled, and EHTR is Set
9.5.4
Burst Transfer
The MPC561/MPC563 uses non-wrapping burst transfers to access operands of up to 32 bytes (eight
words). A non-wrapping burst access stops accessing the external device when the word address is modulo
four/eight. Burst configuration is determined by the value of BURST_EN in the SIUMCR register. See
Chapter 5, “Unified System Interface Unit (USIU) Overview
” for further details. The MPC561/MPC563
begins the access by supplying a starting address that points to one of the words in the array and requires
the memory to sequentially drive or sample each word on the data bus. The selected slave device must
internally increment ADDR28 and ADDR29 (and ADDR30 in the case of a 16-bit port slave device, and
also ADDR31 in the case of an 8-bit port slave device) of the supplied address for each transfer, causing
the address to reach a four/eight word boundary, and then stop. The address and transfer attributes supplied
by the MPC561/MPC563 remain stable during the transfers. The selected device terminates each transfer
by driving or sampling the word on the data bus and asserting TA.
CLKOUT
Data
TA
RD/
WR
Pre-discharge
ADDR[8:31]
TS
Read Cycle
Write Cycle
Write Data
OE
Read Data
EHTR provides 1 clock
gap to three-state data bus
to low voltage
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...