RCS Microsystems M50734 Designers Board — M50734SP microcomputer visible at centre

The original RCS Microsystems marketing data sheet for the Designers Board. Click either page to view full size.

The RCS Microsystems M50734 Designers Board (RCS part no. RCSM 50734) was produced by RCS Microsystems Limited of 141 Uxbridge Road, Hampton Hill, Middlesex, TW12 1BL in May 1987. It was priced at £159.00 ex-VAT (£186 inc. VAT) and designed to enable engineers to be "up-and-running" with the Mitsubishi 740 range of CMOS single-chip microcomputers as quickly as possible.

The board is based on the M50734SP extended microcomputer (the ROM-less, development variant) and is suitable for initial development of all members of the 740 family. It is intended to be connected to a host development system — such as a PC with a suitable assembler — and used via the on-board monitor program to debug downloaded software.

The RS-232 interface connects the M50734SP UART pins to the 9-way D-type connector via Z1 (MC1488P driver) and Z2 (MC1489P receiver). Click to view full size.

The 8K RAM (Z7, 8464A-10L) is protected by a 3.6V NiMH battery (BT1, 110mAh) via diode D2. When mains power is present the RAM is powered from the +5V rail; on power loss the battery takes over via E6, maintaining RAM contents indefinitely. Click to view full size.

Jumper E6 controls whether battery backup is active:

• Position A — Battery backup enabled. When 5V DC power is removed from the board, the RAM is kept alive by BT1, preserving any downloaded programs or data across power cycles.
• Position B — Battery backup disabled. The RAM is not connected to the battery and its contents will be lost when power is removed.

The 2 Kb monitor ROM at $F800–$FEFF provides the following capabilities via a terminal connected to the RS-232 port at 9600 baud, 8N1:

The monitor is started by the '** 740 MON V1.1 **' message and accepts single-character commands enclosed in [cmd] brackets.

View Monitor Disassembly →

Address Range	Use
$FFFF–$FFF4	Reset and interrupt vectors
$FFF3–$FF44	User-available special page
$FF43–$FF00	Monitor fixed entry points
$FEFF–$FE5A	Monitor expansion area
$FE59–$F800	Monitor program (2 Kb ROM)
$F7FF–$C000	User-available EPROM space
$BFFF–$8000	Chip Select 5
$7FFF–$7000	Chip Select 4
$6FFF–$6000	Chip Select 3
$5FFF–$5000	Chip Select 2
$4FFF–$4000	Chip Select 1
$3FFF–$2000	Echo (address mirrors)
$1FFF–$0200	User RAM (8 Kb SRAM with battery backup)
$01FF–$0100	Stack
$00FF–$00DA	Internal registers (CPU peripherals)
$00D9–$00D1	User-available zero page RAM
$00D0–$00B0	Monitor variables
$00AF–$0000	User-available zero page RAM