Manual

Technical Description

Sealevel Systems ACB-104 Page 8

Technical Description

The ACB-104 utilizes the Zilog 85230 Enhanced Serial Communications Controller (ESCC). This chip features

programmable baud rate, data format and interrupt control, as well as DMA control. Refer to the ESCC Users

Manual for details on programming the 85230 ESCC chip.

Features

• One channel of sync/async communications using 85230 chip

• DMA supports data rate greater than 1 million bits per second (bps)

• Selectable Port Address, IRQ level ( 3, 4, 5, 7, 9, 10, 11, 12, 15)

• Selectable DMA channels (0, 1, 2, 3)

• EIA-232 interface with full modem control signals TD, RD, RTS, CTS, DSR, DCD, DTR, TXC, RXC, TSET

signals

• EIA-530 interface with modem control signals TD, RD, RTS, CTS, DTR, TXC, RXC, TSET signals

• Jumper options for Transmit clock as input or output

• Software programmable baud rate

Internal Baud Rate Generator

The baud rate of the ESCC is programmed under software control. The standard oscillator supplied with the board is

7.3728 MHz. However, other oscillator values can be substituted to achieve different baud rates.

Programming the ACB-104

Control/Status Port

The ACB-104 occupies eight input/output (I/O) addresses. The ESCC chip uses the first four, while the fifth

address (Base+4) is the address of the on-board Control/Status Port. This port is used to set the Data Terminal

Ready (DTR) and to enable or disable DMA under program control, and to monitor the Data Set Ready (DSR)

input signals from the modem.

Bit Output Port Bits Input Port Bits

0 DTR A 1=On, 0=Off DSR A 1=Off, 0=On

1 Unused bit Unused bit

2 Unused bit Unused bit

3 Unused bit ESCC INT 1=Off, 0=On

4 Unused bit Unused bit

5 Unused bit TC STAT 1=Off, 0=On

6 Unused bit Unused bit

7 CH. A DMA Enable

ESCC CH.A 1=On, 0=Off

Ch.A DMA 1=Off, 0=On

Software Examples

Function Program Bits

Turn On CH.A DTR Out (Base+4), XXXX XXX1

Turn Off CH.A DTR Out (Base+4), XXXX XXX0

Enable DMA Drivers Out (Base+4), 1XXX XXXX

Disable DMA Drivers Out (Base+4), 0XXX XXXX

Test CH.A DSR In (Base+4), Mask=0000 0001