ZiLOG Z80 Handbook page 254

banks of memory may be alternately connected and disconnected
from the system bus under software control for multiprogramming
or other uses.
TDL SYSTEM MONITOR BOARD
The SMB board is a multipurpose board that provides a monitor,
RAM, and I/O device controllers. The SMB contains a 2K monitor,
the ZAPPLETM monitor in PROM. The monitor is a comprehensive
debug package and collection of software I/O drivers, including a
serial I/O driver and an audio tape-cassette driver. In addition to the
2K of PROM, the SMB contains 2K bytes of RAM, available to the
system user. Two serial I/O ports are available. They can provide
serial I/O at 110 to 9600 baud and interface to either a 20-mA cur-
rent loop, or RS-232 device. Baud rates of 110 (Teletype), 300, 600,
1200, 4800, and 9600 are jumper-selectable. One parallel I/O port is
available to the user and can be software configured to either an
input, or output port.
Courtesy Technical Design Labs, Inc.
Fig. 18 -3. TDL SMBTM board.
A second parallel I/O port (on a Motorola PIA, a programmable
I/O device similar to a PIO) connects to a set of 8-dip switches
which are used to configure the SMB board for I/O. By means of
proper settings on the dip switches, the four system logical devices
can be set to a physical device. The four system logical devices are
the console device, tape-reader device, and listing device. These
263