mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 171

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5.9.1 Chip-Select Registers
5.9.1.1 Chip-Select Pin Assignment Registers
MC68HC16Y3/916Y3
USER’S MANUAL
Each chip-select pin can have one or more functions. Chip-select pin assignment reg-
isters CSPAR[1:0] determine functions of the pins. Pin assignment registers also de-
termine port size (8- or 16-bit) for dynamic bus allocation. A pin data register (PORTC)
latches data for chip-select pins that are used for discrete output.
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[10:0] and CSBARBT). However, because the logic state of ADDR20 is al-
ways the same as the state of ADDR19 in the MCU, the largest usable block size is
512 Kbytes. Multiple chip-selects assigned to the same block of addresses must have
the same number of wait states.
Chip-select option registers (CSORBT and CSOR[0:10]) determine timing of and con-
ditions for assertion of chip-select signals. Eight parameters, including operating
mode, access size, synchronization, and wait state insertion can be specified.
Initialization software usually resides in a peripheral memory device controlled by the
chip-select circuits. A set of special chip-select functions and registers (CSORBT and
CSBARBT) is provided to support bootstrap operation.
Comprehensive address maps and register diagrams are provided in APPENDIX D
REGISTER SUMMARY.
The pin assignment registers contain twelve 2-bit fields that determine the functions of
the chip-select pins. Each pin has two or three possible functions, as shown in Table
5-22.
Table 5-23 shows pin assignment field encoding. Pins that have no discrete output
function must not use the %00 encoding as this will cause the alternate function to be
selected. For instance, %00 for CS0/BR will cause the pin to perform the BR function.
Chip-Select
CSBOOT
Freescale Semiconductor, Inc.
CS10
Table 5-22 Chip-Select Pin Functions
CS0
CS1
CS2
CS3
CS4
CS5
CS6
CS7
CS8
CS9
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Alternate
Function
CSBOOT
ADDR19
ADDR20
ADDR21
ADDR22
ADDR23
BGACK
FC0
FC1
FC2
BR
BG
Discrete
Output
ECLK
PC0
PC1
PC2
PC3
PC4
PC5
PC6
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MOTOROLA
5-63