AN2797 Freescale Semiconductor / Motorola, AN2797 Datasheet - Page 27

• Manufacturer Part Number: AN2797
• Description: Migrating from IBM 750GX to MPC7447A
• Manufacturer: Freescale Semiconductor / Motorola

1.
5.2
One of the changes in terms of hardware between the IBM 750GX and MPC7447A is that the MPC7447A does not
support 3.3V I/O. It only supports 1.8V and 2.5V as shown in
Table 16
contains some optional 60x signals that are not implemented in the MPC7447A all other 60x signals are the same.
Freescale Semiconductor
As in Table 5 – PLL range configuration
Signal Name
TEST[0:3]
TEST[4]
VDD_SENSE
60x Signal Differences
shows some of the differences in 60x signals between the IBM 750GX and MPC7447A. The IBM 750GX
Signal Description
60x bus mode select
Address bus
Address parity
Address parity error
Address bus busy
Transaction burst
Cache inhibited
Write through
Data bus busy
Data bus write only
Data bus disable
Data parity error
Voltage Level
1.8V
2.5V
3.3V
B10, E10
Number
A12, B6,
G13,
D10
N12
Pin
IBM 750GX
BVSEL=0, L1TSTCLK=1
BVSEL=1, L1TSTCLK=1
BVSEL=1, L1TSTCLK=0
Migrating from IBM 750GX to MPC7447A, Rev. 1.0
Table 14. IBM 750GX Additional Signals
Active
Table 15. Supported I/O Voltages
Table 16. 60x Signal Differences
I/O
I
I
TBST (input/output)
ABB (input/output)
DBB (input/output)
IBM 750GX
WT (output)
CI (output)
Description
For internal factory test. Should be pulled up to OVdd for
normal operation.
For internal factory test. Should be pulled down to GND.
Internally connected to OVdd allowing an external device to
know I/O voltage level. (Were OVdd in earlier MPC74xx
implementations)
AP[0:3]
Default
A[0:31]
DBWO
DBDIS
DPE
APE
Table
MPC7447A
BVSEL=0
BVSEL=1
N/A
15.
BMODE0=VDD
BMODE1=VDD
TBST (output)
WT (output)
MPC7447A
CI (output)
AP[1:4]
A[0:35]
N/A
N/A
N/A
N/A
N/A
N/A
1
2
Hardware Considerations
27