MC68HC05L16 Datasheet, PDF (20/146 Pages) Freescale Semiconductor, Inc – Microcontrollers

General Description
1.5.9 Port E (PE0–PE7/FP38–FP35)
Port E is an 8-bit output-only port that shares its bits with LCD frontplane drivers. Port E lines are
configured as LCD outputs during power-on or reset. PE0–PE3 and PE4–PE7 outputs may be configured
as open-drain outputs by a software option.
1.5.10 VLCD1, VLCD2, and VLCD3
These pins provide offset to the LCD driver bias for adjusting the contrast of the LCD.
1.5.11 NDLY
This pin is reserved for factory test and should be connected to V_DD in single-chip mode (user mode).
1.6 Modes of Operation
The MC68HC05L16 has two operating modes:
• Single-chip mode (SCM)
• Self-check mode
Single-chip mode, also called user mode, allows maximum use of pins for on-chip peripheral functions.
The self-check capability of MC68HC05L16 provides an internal check to determine if the device is
functional.
1.6.1 Mode Entry
Mode entry is done at the rising edge of the RESET pin. Once the device enters one of the modes, the
mode cannot be changed by software. Only an external reset can change the mode.
At the rising edge of the RESET pin, the device latches the states of IRQ1 and IRQ2 and places itself in
the specified mode. While the RESET pin is low, all pins are configured as single-chip mode. Table 1-2
shows the states of IRQ1 and IRQ2 for each mode entry.
High voltage V_TST = 2 x V_DD is required to select modes other than single-chip mode.
Table 1-2. Mode Select Summary
Modes
RESET
PC6/IRQ1
Single-Chip (User) Mode
Self-Check Mode
V_SS or V_DD
V_TST
PC7/IRQ2
V_SS or V_DD
V_DD
MC68HC05L16 • MC68HC705L16 Data Sheet, Rev. 4.1
20
Freescale Semiconductor