Chapter 21 External Bus Interface (S12XEBIV2)
MC9S12XDP512 Data Sheet, Rev. 2.17
794
Freescale Semiconductor
21.4
Functional Description
This section describes the functions of the external bus interface. The availability of external signals and
functionsinrelationtotheoperatingmodeisinitiallysummarizedanddescribedinmoredetailinseparate
sub-sections.
21.4.1
Operating Modes and External Bus Properties
A summary of the external bus interface functions for each operating mode is shown in
Table 21-7
.
Table 21-7. Summary of Functions
Properties
(if Enabled)
Single-Chip Modes
Expanded Modes
Normal
Single-Chip
Special
Single-Chip
Normal
Expanded
Emulation
Single-Chip
Emulation
Expanded
Special
Test
Timing Properties
PRR access
1
1
Incl. S12X_EBI registers
2
Refer to S12X_MMC section.
3
If EWAITE = 1, the minimum number of external bus cycles is 3.
4
Available only if configured appropriately by ROMON and EROMON (refer to S12X_MMC section).
2 cycles
read internal
write internal
2 cycles
read internal
write internal
2 cycles
read internal
write internal
2 cycles
read external
write int & ext
2 cycles
read external
write int & ext
2 cycles
read internal
write internal
Internal access
visible externally
—
—
—
1 cycle
1 cycle
1 cycle
External
address access
and
unimplemented area
access
2
—
—
Max. of 2 to 9
programmed
cycles
or n cycles of
ext. wait
3
1 cycle
Max. of 2 to 9
programmed
cycles
or n cycles of
ext. wait
3
1 cycle
Flash area
address access
4
—
—
—
1 cycle
1 cycle
1 cycle
Signal Properties
Bus signals
—
—
ADDR[22:1]
DATA[15:0]
ADDR[22:20]/A
CC[2:0]
ADDR[19:16]/
IQSTAT[3:0]
ADDR[15:0]/
IVD[15:0]
DATA[15:0]
ADDR[22:20]/A
CC[2:0]
ADDR[19:16]/
IQSTAT[3:0]
ADDR[15:0]/
IVD[15:0]
DATA[15:0]
ADDR[22:0]
DATA[15:0]
Data select signals
(if 16-bit data bus)
—
—
UDS
LDS
ADDR0
LSTRB
ADDR0
LSTRB
ADDR0
LSTRB
Data direction signals
—
—
RE
WE
R/W
R/W
R/W
External wait
feature
—
—
EWAIT
—
EWAIT
—
Reduced input
threshold enabled on
—
—
Refer to
Table 21-3
DATA[15:0]
EWAIT
DATA[15:0]
EWAIT
Refer to
Table 21-3