Serial Communications; Digital Signal Processor; Serial Communications Circuitry - HP PageWriter XL M1705B Service Manual

Serial Communications
The other important element in the I/O control circuitry is the
serial communications block (shown in Figure 5-7), which provides
asynchronous serial communication for direct connect or modem.
The universal asynchronous receiver/transmitter (UART) circuit
provides buffering, parity, handshake logic, interrupt capabilities, and
parallel-to-serial conversions for sending and receiving RS-232 data.
The driver/receiver circuit converts serial signals between RS-232
voltage levels and TTL levels.
RS-232
CONNECTOR
BAUD RATES
INTERRUPTS
TO PI0 4
M1700-03
Figure 5-7. Serial Communications Circuitry.
Digital Signal Processor
The digital signal processor (DSP) assembly consists of a Motorola
56001@ digital signal processor and three static RAMS that provide
32K words (24 bits-per-word) of memory. R.efer to Figure 5-S.
The DSP provides a high-speed, synchronous interface for 24-bit
serial data from the patient module, and digital filters for ECG data.
5-14 Theory of Operation