C6850
Asynchronous Communications Interface
Synthesizable Core
Function Description
The C6850 asynchronous communications interface (ACIA) core provides data formatting
and control to the asynchronous data communications of data bus systems.
The core has select, enable, read/write, interrupt and bus interface logic features
that allow data transfers over an 8-bit bi-directional parallel data bus system. With
proper formatting and error checking, the core can transmit and receive serial data.
In addition, a programmable control register provides the core with a transmit control,
a receive control, an interrupt control, variable word lengths and clock division ratios.
Three control lines are provided for peripheral or modem operation.
Features
- Programmable data word length, parity and stop bits
- Parity, overrun and framing error checking instructions and counting loop interactions
- Supports transmission rates over the 1.0 Mbps spec
- False start bit deletion
- Peripheral modem control functions
- The C6850 was developed in VHDL and synthesizes to approximately 1,300 gates depending
on the process used
- Functionality based on the Motorola MC6850
Symbol

Pin Description
Name |
Type |
Polarity |
Description |
EXT_RST |
In |
High |
External Reset |
TX_CLK |
In |
- |
Transmit Clock |
RX_CLK |
In |
- |
Receive Clock |
RXW |
In |
- |
Read/Write |
CSn |
In |
Low |
Chip Select |
RS |
In |
Low |
Register Select |
E |
In |
- |
Enable (clock) |
DIN [7:0] |
In |
Low |
Data Input Bus |
RXDATA |
In |
- |
Receive Data |
CTSn |
In |
Low |
Clear - to - Send |
DCDn |
In |
Low |
Data Carrier Direct |
IRQn |
Out |
Low |
Interrupt Request |
TXDATA |
Out |
- |
Transmit Data |
RTSn |
Out |
Low |
Request - to - Send |
DO [7:0] |
Out |
Low |
Data Output Bus |
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