MC7447AHX1420LB Freescale Semiconductor, MC7447AHX1420LB Datasheet - Page 40

• Manufacturer Part Number: MC7447AHX1420LB
• Description: IC MPU RISC 1420MHZ 360-FCCBGA
• Manufacturer: Freescale Semiconductor

Specifications of MC7447AHX1420LB

• Processor Type: MPC74xx PowerPC 32-Bit
• Speed: 1.42GHz
• Voltage: 1.3V
• Mounting Type: Surface Mount
• Package / Case: 360-FCCBGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -

System Design Information
During inactive periods on the bus, the address and transfer attributes may not be driven by any master and
may, therefore, float in the high-impedance state for relatively long periods of time. Because the
MPC7447A must continually monitor these signals for snooping, this float condition may cause excessive
power draw by the input receivers on the MPC7447A or by other receivers in the system. These signals
can be pulled up through weak (10-KΩ) pull-up resistors by the system, address bus driven mode enabled
(see the MPC7450 RISC Microprocessor Family Users’ Manual for more information on this mode), or
they may be otherwise driven by the system during inactive periods of the bus to avoid this additional
power draw. Preliminary studies have shown the additional power draw by the MPC7447A input receivers
to be negligible and, in any event, none of these measures are necessary for proper device operation. The
snooped address and transfer attribute inputs are: A[0:35], AP[0:4], TT[0:4], CI, WT, and GBL.
If address or data parity is not used by the system, and respective parity checking is disabled through HID1,
the input receivers for those pins are disabled and do not require pull-up resistors, and may be left
unconnected by the system. If extended addressing is not used (HID0[XAEN] = 0), A[0:3] are unused and
must be pulled low to GND through weak pull-down resistors; additionally, if address parity checking is
enabled (HID1[EBA] = 1) and extended addressing is not used, AP[0] must be pulled up to OV
through
DD
a weak pull-up resistor. If the MPC7447A is in 60x bus mode, DTI[0:3] must be pulled low to GND
through weak pull-down resistors.
The data bus input receivers are normally turned off when no read operation is in progress and, therefore,
do not require pull-up resistors on the bus. Other data bus receivers in the system, however, may require
pull-ups, or that those signals be otherwise driven by the system during inactive periods. The data bus
signals are: D[0:63] and DP[0:7].
9.7
JTAG Configuration Signals
Boundary-scan testing is enabled through the JTAG interface signals. The TRST signal is optional in the
IEEE 1149.1 specification but is provided on all processors that implement the PowerPC architecture.
While it is possible to force the TAP controller to the reset state using only the TCK and TMS signals, more
reliable power-on reset performance will be obtained if the TRST signal is asserted during power-on reset.
Because the JTAG interface is also used for accessing the common on-chip processor (COP) function,
simply tying TRST to HRESET is not practical.
The COP function of these processors allows a remote computer system (typically a PC with dedicated
hardware and debugging software) to access and control the internal operations of the processor. The COP
interface connects primarily through the JTAG port of the processor, with some additional status
monitoring signals. The COP port requires the ability to independently assert HRESET or TRST in order
to fully control the processor. If the target system has independent reset sources, such as voltage monitors,
watchdog timers, power supply failures, or push-button switches, then the COP reset signals must be
merged into these signals with logic.
The arrangement shown in
Figure 19
allows the COP port to independently assert HRESET or TRST,
while ensuring that the target can drive HRESET as well. If the JTAG interface and COP header will not
be used, TRST should be tied to HRESET through a 0-Ω isolation resistor so that it is asserted when the
system reset signal (HRESET) is asserted, ensuring that the JTAG scan chain is initialized during
power-on. Although Freescale recommends that the COP header be designed into the system as shown in
Figure
19, if this is not possible, the isolation resistor will allow future access to TRST in the case where
a JTAG interface may need to be wired onto the system in debug situations.
MPC7447A RISC Microprocessor Hardware Specifications, Rev. 5
40
Freescale Semiconductor