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AST RESEARCH, INC. TECHNICAL BULLETIN #0610 02-07-90
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SERIAL PORT PARITY ERRORS
Under certain circumstances, the serial ports on some Premium computers may
exhibit parity errors during serial data transmission. The problem manifests
itself as a bad parity bit when transmitting data with 8 Bits, 1 Stop Bit and
Even Parity.
The problem is caused by an anomaly in the Zymos 16C451 and 16C452 Dual UART
serial controller chips that were once used on some Premium motherboards.
Users experiencing this problem can resolve the problem in either of the
following ways:
1. Change the data transmission parameters from; 8 Bits, 1 Stop Bit, Even
Parity, to; 8 Bits, 1 Stop Bit No Parity.
2. Contact your AST Authorized Service Center and arrange for the
replacement of the system's motherboard.
ASSEMBLIES AFFECTED:
Chip Identification: Chips can be identified by observing the soldered-in
chips at the following locations. These chips will
be labeled either, "ZYMOS 16C451" or "ZYMOS
16C452".
AST
DESCRIPTION PART NUMBER CHIP LOCATION
PCB Premium Motherboard 202273-00X U104
PCB Premium Motherboard 202356-00X U104
PCB WS 386SX Motherboard 202276-00X U123
PCB Bravo 386SX Motherboard 202343-00X U9
PCB Bravo 286 Motherboard 202286-00X U6