Freescale Semiconductor MPC5553 - External Signal Description

MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
12-6 Freescale Semiconductor
12.1.4.4 Configurable Bus Speed Modes
In all supported bus speed modes, the external CLKOUT frequency is divided down from the internal
system clock. The EBI behavior remains dictated by the mode of the EBI, except that the EBI drives and
samples signals at the scaled CLKOUT rather than the internal system clock. The bus speed mode is
selected by writing the external clock control register in the system integration module (SIU_ECCR). The
EBI supports both 1/2 or 1/4 speed modes, meaning that the external CLKOUT frequency is scaled down
(by 2 or 4) compared with that of the internal system clock, which is unchanged.
NOTE
In a multi-master system (where the PLL is in dual-controller mode) only
1/2 speed mode is supported.
12.1.4.5 16-Bit Data Bus Mode
For MCUs that have only 16 data bus signals pinned out, or for systems where the use of a different
multiplexed function (e.g. GPIO) is desired on 16 of the 32 data pins, the EBI supports a 16-bit data bus
mode. In this mode, DATA[0:15] are the only data signals used by the EBI.
For EBI-mastered accesses, the operation in 16-bit data bus mode (EBI_MCR[DBM] = 1,
EBI_BRn[PS] = x) is similar to a chip select access to a 16-bit port in 32-bit data bus mode
(EBI_MCR[DBM] = 0, EBI_BRn[PS] = 1), except for the case of an EBI-mastered non-chip select access
of exactly 32-bit size.
External master accesses and EBI-mastered non-chip select accesses of exactly 32-bit size are supported
via a two (16-bit) beat burst for both reads and writes. See Section 12.4.2.11, “Non-Chip-Select Burst in
16-bit Data Bus Mode.” Non-chip select transfers of non-32-bit size are supported in standard non-burst
fashion.
16-bit data bus mode is entered when EBI_MCR[DBM] = 1. Note that DBM = 0 out of reset.
12.1.4.6 Debug Mode
When the MCU is in debug mode, the EBI behavior is unaffected and remains dictated by the mode of the
EBI.
12.2 External Signal Description
Table 12-3 alphabetically lists the external signals used by the EBI.
Table 12-3. Signal Properties
Name I/O Type Function Pull
1
MPC5553
Packages
MPC5554
Package
ADDR[8:11] I/O Address Bus — 416
Ye s
ADDR[12:31]
2
I/O Address Bus — 416, 324
BB I/O Bus Busy Up None Yes
BG I/O Bus Grant Up None Yes
BR
I/O Bus Request Up None Yes
BDIP Output Burst Data in Progress Up 416, 324 Yes