MC68HC912BD32CFU10 FREESCALE [Freescale Semiconductor, Inc], MC68HC912BD32CFU10 Datasheet - Page 65

• Manufacturer Part Number: MC68HC912BD32CFU10
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

7-bus
NECLK — No External E Clock
LSTRE — Low Strobe (LSTRB) Enable
RDWE — Read/Write Enable
In expanded modes, writes to this bit have no effect. E clock is
required for de-multiplexing the external address; NECLK will remain
zero in expanded modes. NECLK can be written once in normal single
chip mode and can be written anytime in special single chip mode.
The bit can be read anytime.
Normal: write once; Special: write anytime except the first time. Read
anytime. This bit has no effect in single-chip modes or normal
expanded narrow mode.
LSTRB is used during external writes. After reset in normal expanded
mode, LSTRB is disabled. If needed, it should be enabled before
external writes. External reads do not normally need LSTRB because
all 16 data bits can be driven even if the MCU only needs 8 bits of
data.
TAGLO is a shared function of the PE3/LSTRB pin. In special
expanded modes with LSTRE set and the BDM instruction tagging
on, a zero at the falling edge of E tags the instruction word low byte
being read into the instruction queue.
Normal: write once; Special: write anytime except the first time. Read
anytime. This bit has no effect in single-chip modes.
Freescale Semiconductor, Inc.
For More Information On This Product,
0 = PE4 is the external E-clock pin subject to the following
1 = PE4 is a general-purpose I/O pin.
0 = PE3 is a general-purpose I/O pin.
1 = PE3 is configured as the LSTRB bus-control output, provided
0 = PE2 is a general-purpose I/O pin.
1 = PE2 is configured as the R/W pin. In single chip modes, RDWE
limitation: In single-chip modes, PE4 is general-purpose I/O
unless NECLK = 0 and either IVIS = 1 or ESTR = 0. A 16-bit
write to PEAR:MODE can configure all three bits in one
operation.
the MCU is not in single chip or normal expanded narrow
modes.
has no effect and PE2 is a general-purpose I/O pin.
Bus Control and Input/Output
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Bus Control and Input/Output
MC68HC912BD32 Rev 1.0
Registers