Datasheet
MC68332 MOTOROLA
MC68332TS/D 31
3.5.1 Chip-Select Registers
Pin assignment registers CSPAR0 and CSPAR1 determine functions of chip-select pins. These regis-
ters also determine port size (8- or 16-bit) for dynamic bus allocation.
A pin data register (PORTC) latches discrete output data.
Blocks of addresses are assigned to each chip-select function. Block sizes of 2 Kbytes to 1 Mbyte can
be selected by writing values to the appropriate base address register (CSBAR). Address blocks for
separate chip-select functions can overlap.
Chip-select option registers (CSORBT and CSOR[10:0]) determine timing of and conditions for asser-
tion of chip-select signals. Eight parameters, including operating mode, access size, synchronization,
and wait state insertion can be specified.
Initialization code often resides in a peripheral memory device controlled by the chip-select circuits. A
set of special chip-select functions and registers (CSORBT, CSBARBT) is provided to support bootstrap
operation.
3.5.2 Pin Assignment Registers
The pin assignment registers (CSPAR0 and CSPAR1) contain pairs of bits that determine the function
of chip-select pins. The pin assignment encodings used in these registers are shown below.
CSPAR0 contains seven 2-bit fields that determine the functions of corresponding chip-select pins.
CSPAR0[15:14] are not used. These bits always read zero; writes have no effect. CSPAR0 bit 1 always
reads one; writes to CSPAR0 bit 1 have no effect.
Table 12 Pin Assignment Encodings
Bit Field Description
00 Discrete Output
01 Alternate Function
10 Chip Select (8-Bit Port)
11 Chip Select (16-Bit Port)
CSPAR0 —Chip Select Pin Assignment Register 0 $YFFA44
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 CSPA0[6] CSPA0[5] CSPA0[4] CSPA0[3] CSPA0[2] CSPA0[1] CSBOOT
RESET:
0 0 DATA2 1 DATA2 1 DATA2 1 DATA1 1 DATA1 1 DATA1 1 1 DATA0
Table 13 CSPAR0 Pin Assignments
CSPAR0 Field Chip Select Signal Alternate Signal Discrete Output
CSPA0[6] CS5
FC2 PC2
CSPA0[5] CS4
FC1 PC1
CSPA0[4] CS3
FC0 PC0
CSPA0[3] CS2
BGACK —
CSPA0[2] CS1
BG —
CSPA0[1] CS0
BR —
CSBOOT
CSBOOT ——
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