Low Voltage RESET
A DS1813, low-voltage supervisor at LV1 protects the APS12DT256SLK under-voltage conditions.
LV1 will assert RESET when the 5V rail falls below the trip point of 4.62V. LV1 will assert RESET for
approximately 150ms after voltage returns to nominal.
TIMING
Timing input to the MCU is provided by a 4 MHz, fundamental frequency, crystal oscillator. The
oscillator exhibits a frequency tolerance of ±30ppm. The timing input is configured for full-
swing Pierce mode operation in both MCU configurations.
The XCLKS output is routed to test point VIA located near the MCU. The internal clock
ECLKX2 is available at this via if needed.
COMMUNICATIONS
The APS12DT256SLK module provides the user with 1 COM port and 1 CAN port on the
module. COM1 is links to SCI0 on the MCU. The RS-232 channel is configured as a DCE
device. This allows a straight through cable between the module and the host PC.
Also, the MCU provides 2 additional CAN ports, 2 SPI ports, and 1IIC port. Access to these
communications ports is provided through connector J1. Physical layer support is not provide
for these feature and must be provided by the user in needed. Refer to the MCU Device User
Guide for details
RS-232
An RS-232 translator provides RS-232 to TTL/CMOS logic level translation on the COM
connector. The COM connector is a 9-pin Dsub, right-angle connector. A ferrite bead on
shield ground provides conducted immunity protection. Communication signals TXD and RXD
are routed from the transceiver to the MCU. Communications signals TXD and RXD also
connect to general purpose Port S signals on the MCU.
Table 2: COM Connections
MCU Port
COM Signal
I/O PORT
CONNECTOR
PS1/TXD0 TXD0
J1-5
PS0/RXD0 RXD1
J1-7
PS3/TXD1 TXD1
J1-40
PS2/RSXD1 RXD1
J1-38
12 Freescale Semiconductor
