mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 110

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

5.2 System Configuration
5-2
MOTOROLA
Although the full IMB supports 24 address and 16 data lines, MC68HC16Y3/916Y3
MCUs use only 20 address lines. Because the CPU16 uses only 20 address lines.
ADDR[23:20] follow the state of ADDR19.
Operating mode is determined by the logic states of specific MCU pins during reset.
Refer to 5.7.3 Operating Configuration Out of Reset for more detailed information.
The MCU can operate as a stand-alone device (single-chip mode), with a 20-bit
external address bus and an 8-bit external data bus, or with a 20-bit external address
bus and a 16-bit external data bus. SCIM2 pins can be configured for use as I/O ports
or programmable chip select signals. Refer to 5.9 Chip-Selects and 5.10 General Pur-
pose Input/Output for more information. System configuration is determined by setting
bits in the SCIM2 configuration register (SCIMCR), and by asserting MCU pins during
reset. The following paragraphs describe those configuration options controlled by
SCIMCR.
• Single-chip mode, in which the SCIM2 provides seven general purpose I/O ports,
no external address or data buses, one general purpose chip-select line, and a
boot ROM chip-select line.
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 5-1 SCIM2 Block Diagram
Go to: www.freescale.com
EXTERNAL BUS INTERFACE
SYSTEM CONFIGURATION
CLOCK SYNTHESIZER
SYSTEM PROTECTION
FACTORY TEST
CHIP SELECTS
MODCLK
TSC
XTAL
CLKOUT
EXTAL
CHIP SELECTS
EXTERNAL BUS
FREEZE/QUOT
RESET
MC68HC16Y3/916Y3
USER’S MANUAL
S(C)IM BLOCK