Hardware information – Quatech DSP-100 User Manual

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10. Hardware Information

The DSP-100's two asynchronous serial ports are implemented using 2 standard 16C550
UARTs. Each of these UARTs requires 8 bytes of I/O space. The DSP-100's serial ports
are addressable in two modes:

1. 'Block Mode' : The two serial ports are configured in one 16-byte continuous

block of I/O address space. The block must begin on an even 16-byte (10H)
boundary (e.g. 300H, 310H, 320H, etc.).

Base Address + 8

Channel B

Base Address + 0

Channel A

Address assignment

DSP-100 RS-232 channel

Figure 5. Block Mode Addressing.

2. 'COM Mode' : The two serial ports are configured at the standard COM port

I/O address locations. The ports may be configured as COM1 and COM3; or
as COM2 and COM4.

Each 16C550 UART contains 8 I/O registers. The last of these registers, located at (Base
address + 7), is referred to as the 'Scratchpad Register' and provides no functionality to
the UART. In place of this Scratchpad Register, the DSP-100 implements an interrupt
status register which can be accessed at (Base address + 7) of any UART.

Intr A

Intr B

Figure 6. Interrupt Status Register.

When one or more UARTs have interrupts pending, the associated bit(s) in the
interrupt status register are set to logic 1. When all the pending interrupts have been
serviced for a specific UART, its interrupt status bit will be cleared to logic 0
automatically. When all the pending interrupts from all UARTs have been serviced,
the entire interrupt status register will return logic 0. The application program should
not exit its interrupt service routine until all pending interrupts from all channels have
been serviced (interrupt status register = 0) or no additional interrupts will be received.

If an application requires the UARTs' Scratchpad Registers, the interrupt status register
can be disabled. Disabling the interrupt status register is supported by the DSP-200
configuration software, which is operating system dependent. Refer to the relevant
operating system installation section for specific usage of this feature.

DSP-100 User's Manual