MC68HC16Z1 Datasheet, PDF (65/500 Pages) Freescale Semiconductor, Inc – M68HC16Z Series

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SM — Saturate Mode Bit
When SM is set and either EV or MV is set, data read from AM using TMER or TMET
is given maximum positive or negative value, depending on the state of the AM sign
bit before overflow.
PK[3:0] — Program Counter Address Extension Field
This field is concatenated with the program counter to form a 20-bit address.
4.2.6 Address Extension Register and Address Extension Fields
There are six 4-bit address extension fields. EK, XK, YK, and ZK are contained by the
address extension register (K), PK is part of the CCR, and SK stands alone.
Extension fields are the bank portions of 20-bit concatenated bank:byte addresses
used in the CPU16 linear memory management scheme.
All extension fields except EK correspond directly to a register. XK, YK, and ZK extend
registers IX, IY, and IZ. PK extends the PC; and SK extends the SP. EK holds the four
MSB of the 20-bit address used by the extended addressing mode.
4.2.7 Multiply and Accumulate Registers
The multiply and accumulate (MAC) registers are part of a CPU submodule that per-
forms repetitive signed fractional multiplication and stores the cumulative result. These
operations are part of control-oriented digital signal processing.
There are four MAC registers. Register H contains the 16-bit signed fractional multipli-
er. Register I contains the 16-bit signed fractional multiplicand. Accumulator M is a
specialized 36-bit product accumulation register. XMSK and YMSK contain 8-bit mask
values used in modulo addressing.
The CPU16 has a special subset of signal processing instructions that manipulate the
MAC registers and perform signal processing calculations.
4.3 Memory Management
The CPU16 provides a 1-Mbyte address space. There are 16 banks within the address
space. Each bank is made up of 64 Kbytes addressed from $0000 to $FFFF. Banks
are selected by means of the address extension fields associated with individual
CPU16 registers.
In addition, address space can be split into discrete 1-Mbyte program and data spaces
by externally decoding the MCU’s function code outputs. When this technique is used,
instruction fetches and reset vector fetches access program space, while exception
vector fetches (other than for reset), data accesses, and stack accesses are made in
data space.
M68HC16 Z SERIES
CENTRAL PROCESSOR UNIT
USER’S MANUAL
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