Embedded Pentium® Processor-Based POS Terminal Sample Design

COM2 is shared with the Infrared interface. IRTX2 and IRRX2 of the ultra I/O directly connect TXD and RXD of the TEMIC TFDU4100 Infrared Transceiver respectively. The functionality of this COM port must be switched in the BIOS. The board uses the FDC37B78x’s alternate IRTX2 and IRRX2 pins, allowing BIOS to switch from COM2 to the Infrared interface.

6.4.4Parallel Port Controller

The parallel port controller is compatible with the IBM PC XT/AT. It supports the optional PS/2- type bi-directional parallel port (SPP) mode, the Enhanced Parallel Port (EPP) mode, and the Extended Capabilities Port (ECP) mode.

6.4.5Keyboard and Mouse

The universal keyboard controller uses an 8042 microcontroller processor core.

6.4.5.1Design Note for Ultra I/O

Each power pin must be individually decoupled with a 0.1 µF capacitor. Since the real time clock on the ultra I/O is not used, VBAT must be tied to ground. If not grounded, this pin may float and confuse the internal circuitry that is trying to detect whether power is valid.

The ultra I/O provides a BIOS interface. This is not implemented on the board, therefore ROMCS# must be pulled high to disable the ROM buffers and avoid interference with the boot ROM.

The SYSOPT pin is latched on the falling edge of RESET_DRV or on VCC Power On Reset to determine the configuration register’s base address. The SYSOPT pin is used to select the CONFIG PORT’s I/O address at power-up. Once powered up, the configuration power base address can be changed through configuration registers. See Table 6 for SYSOPT settings.

Table 6. SYSOPT Pin Settings

Note: If using TTL RS232 drivers, use a 1 KΩ pull-down resistor. If using CMOS RS232 drivers, use 10 KΩ pull-down resistor. The board uses TTL drivers, therefore SYSOPT should be pulled down with a 10 KΩ pull-up resistor. Therefore, the CONFIG PORT and INDEX PORT for the FDC37B78x is located at 0x0370h after Reset.

The setting on SYSOPT must be different then SYSOPT on the SMSC FDC37C669 Super I/O in order for the two chips to configure at different addresses. On the board, FDC37C669 SYSOPT is pulled low with a 1-KΩ resistor. Therefore the FDC37C669 is located at 0x0370h in memory after reset. The two options are given in Table 7.