SKU: ZBX-351
ZBX-351 SERIAL I/O MODULE
The ZBX-351 serial I/O module provides one serial communications channel utilizing an 8251A programmable communications inter- ace. The communications channel may configured as RS-232C or RS-449/422. A split card edge connector allows for a 25 or 37 conductor data cable. In addition, the ZBX-351 contains two general purpose programmable 16-bit BCD or binary timers/event counters.
Communications Interface
The ZBX-351 contains an 8251A USART to control the serial communications interface. The 8251A is programmed by the CPU to operate using virtually any serial data transmission technique presently in use, including IBM bi-sync. The USART accepts data from the CPU in parallel format and converts it into a continuous serial data stream for transmission. It can simultaneously receive serial data streams and convert them into parallel characters for the CPU. The USART will signal the CPU when it can accept a new character for transmission or has a character to send to the CPU. The 8251A contains a number of advanced features including double-buffer data paths with separate I/O registers for control status, data in and data out. The 8251 A is easily programmed using instruction words which specify mode and command instructions. The mode of operation (synchronous or asynchronous), data format, control character for mat, parity, and baud rate are all programmed using instruction words. The 8251A provides full duplex, double buffered transmit and receive capabilities.
16-bit Timers
The ZBX-351 contains an 8253 programmable interval timer which provides three fully programmable and independent BCD and binary interval timers. One timer is utilized to provide a baud rate clock to the USART and the other two are available to the user. The routing of these timer outputs is jumper selectable to the host baseboard.
Interrupt requests are available from up to four sources including two from the USART when a character is ready for transfer to the CPU or when a character is transmitted. The other two interrupt sources are jumper selectable requests generated by the programmable timers.
TECHNICAL SPECIFICATIONS
Word Size
8 bits
Serial Communication
Synchronous
5 to 8 bit characters; internal character synchro nization; automatic sync insertion; even, odd, or no parity generation/detection.
Asynchronous
5 to 8 bit characters; break generation/detection;1, 1 1/2, or 2 stop bits; false start bit detection; even, odd, or no parity generation/detection.
I/O Addressing
8251A USARTRead/Write Data x0, x2, x4 or x6Read StatusWrite Command x1, x3, x5 or x7
8253 PIT
Read/Write Counter 0 x8 or xCRead/Write Counter 1 x9 or xDRead/Write Counter 2 xA or xEWrite Control xB or xF
Note: "x" indicates a base port address which is determined by the host baseboard. Refer to the baseboard hardware reference manual for specifics.
Interval Timer and Baud Rate Generator
Input Frequency
1.23 MHz or 153.6 kHz selectable
Output Frequency
Rate Generator Real time Interrupt(Frequency) (Interval)
Single Timer 2.43 Hz 76.8 kHz 13.0 usec 426.7 msec
Dual Timer 358E-7 Hz 38.4 kHz 26.0 usec 7.77 hrs
Interfaces
ZBX Bus
All signals TTL compatible and per Intel SBX busspecification
Serial Configurable for EIA standard
RS232C orRS449/422
Physical
Width: 2.5 inches (6.4 cm)Length: 3.7 inches (9.40 cm)
Height: 1.06 inches (2.7 cm) ZBX-351 only1.25 inches (3.2 cm) including baseboard
Weight: 1.8 oz. (52 gm); 1 lb. shipping weight
Environmental: 0 to 55 degrees C, 5-95% RH (no condensation)
Power Requirements (Typical)
RS232C +5V 460 mA, +12V 30 mA, -12V 30 mA
RS449 +5V 530 mA
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