![](http://datasheet.mmic.net.cn/370000/P9S12XEP100J1VVLR_datasheet_16728329/P9S12XEP100J1VVLR_243.png)
Chapter 5 External Bus Interface (S12XEBIV4)
MC9S12XE-Family Reference Manual Rev. 1.07
Freescale Semiconductor
243
Table 5-1. External System Signals Associated with XEBI
Signal
I
1
/O
1
All inputs are capable of reducing input threshold level
2
Time-multiplex means that the respective signals share the same pin on chip level and are active alternating in a dedicated
time slot (in modes where applicable).
3
Function-multiplex means that one of the respective signals sharing the same pin on chip level continuously uses the pin
depending on configuration and reset state.
EBI Signal
Multiplex
(T)ime
2
(F)unction
3
Description
Available in Modes
NS
SS
NX
ES
EX
ST
RE
O
—
—
Read Enable, indicates external read access
No
No
Yes
No
No
No
ADDR[22:20]
O
T
—
External address
No
No
Yes
Yes
Yes
Yes
ACC[2:0]
O
—
Access source
No
No
No
Yes
Yes
Yes
ADDR[19:16]
O
T
—
External address
No
No
Yes
Yes
Yes
Yes
IQSTAT[3:0]
O
—
Instruction Queue Status
No
No
No
Yes
Yes
Yes
ADDR[15:1]
O
T
—
External address
No
No
Yes
Yes
Yes
Yes
IVD[15:1]
O
—
Internal visibility read data
No
No
No
Yes
Yes
Yes
ADDR0
O
T
F
External address
No
No
No
Yes
Yes
Yes
IVD0
O
Internal visibility read data
No
No
No
Yes
Yes
Yes
UDS
O
—
Upper Data Select, indicates external access
to the high byte DATA[15:8]
No
No
Yes
No
No
No
LSTRB
O
—
F
Low Strobe, indicates valid data on DATA[7:0]
No
No
No
Yes
Yes
Yes
LDS
O
—
Lower Data Select, indicates external access
to the low byte DATA[7:0]
No
No
Yes
No
No
No
RW
O
—
F
Read/Write, indicates the direction of internal
data transfers
No
No
No
Yes
Yes
Yes
WE
O
—
Write Enable, indicates external write access
No
No
Yes
No
No
No
CS[3:0]
O
—
—
Chip select
No
No
Yes
No
Yes
No
DATA[15:8]
I/O
—
—
Bidirectional data (even address)
No
No
Yes
Yes
Yes
Yes
DATA[7:0]
I/O
—
—
Bidirectional data (odd address)
No
No
Yes
Yes
Yes
Yes
EWAIT
I
—
—
External control for external bus access
stretches (adding wait states)
No
No
Yes
No
Yes
No