MC9S12T64 Datasheet, PDF (111/608 Pages) Motorola, Inc – Specification

Freescale Semiconductor, Inc.
Operating Modes
Operating Modes
Emulation
Expanded Narrow
Mode
Expanded narrow modes are intended to allow connection of single 8-bit
external memory devices for lower cost systems that do not need the
performance of a full 16-bit external data bus. Accesses to internal
resources that have been mapped external (i.e. PORTA, PORTB,
DDRA, DDRB, PORTE, DDRE, PEAR, PUCR, RDRIV) will be accessed
with a 16-bit data bus on Ports A and B. Accesses of 16-bit external
words to addresses which are normally mapped external will be broken
into two separate 8-bit accesses using Port A as an 8-bit data bus.
Internal operations continue to use full 16-bit data paths. They are only
visible externally as 16-bit information if IVIS=1.
Ports A and B are configured as multiplexed address and data output
ports. During external accesses, address A15, data D15 and D7 are
associated with PA7, address A0 is associated with PB0, and data D8
and D0 are associated with PA0. During internal visible accesses and
accesses to internal resources that have been mapped external,
address A15 and data D15 are associated with PA7, and address A0
and data D0 are associated with PB0.
The bus control related pins in Port E (PE7/NOACC,
PE6/MODB/IPIPE1, PE5/MODA/IPIPE0, PE4/ECLK,
PE3/LSTRB/TAGLO, and PE2/R/W) are all configured to serve their bus
control output functions rather than general purpose I/O. Notice that
writes to the bus control enable bits in the PEAR register in emulation
mode are restricted.
The main difference between emulation modes and normal modes is
that some of the bus control and system control signals cannot be written
in emulation modes.
Operating Modes
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MC9S12T64Revision 1.1.1