8052.com SBC Technical Details Quick Reference

8052.com SBC - Technical Details Quick Reference SBC Hardware: Main | SBC Schematic/Parts List | Technical Details | All pages in PDF format
SBC In-System Programming: Information | VisISP-52 ISP Application
SBCMON Monitor/Operating System: Main Page | Manual
SBCMON-based Software: SBCMON Monitor | Keypad Demo | LCD Echo Demo | Hardware Clock | Software Clock
SBCMON-based PS/2 Software: PS/2 Comm Monitor | PS/2 Keyboard | PS/2 Mouse
ORDER 8052.com SBC: PCB, KIT OR BUILT SBC AVAILABLE FOR PURCHASE

Microcontroller Port Pin Usage

Name	Pin	Function/Connection
Port 1
P1.0	1	LED/Direct LCD DB0. Used to control the D6 LED if JP1 is connected. Also used as DB0 when the LCD is connected as a direct-connection.
P1.1	2	I2C SDA/Direct LCD DB1. Used as the SDA line to access the DS1307 via I2C. Also used as DB1 when the LCD is connected as a direct-connection.
P1.2	3	I2C SCL/Direct LCD DB2. Used as the SCL line to access the DS1307 via I2C. Also used as DB2 when the LCD is connected as a direct-connection.
P1.3	4	Direct LCD DB3. Used as DB2 when the LCD is connected as a direct-connection.
P1.4	5	SPI SS/Direct LCD DB4. Used to select the AT25010A for SPI access. Also used as DB4 when the LCD is connected as a direct-connection.
P1.5	6	SPI MOSI/Direct LCD DB5. Used as MOSI when communicating with the AT25010A via SPI and when in AT89S8252 ISP mode. Also used as DB5 when the LCD is connected as a direct-connection.
P1.6	7	SPI MISO/Direct LCD DB6. Used as MISO when communicating with the AT25010A via SPI and when in AT89S8252 ISP mode. Also used as DB6 when the LCD is connected as a direct-connection.
P1.7	8	SPI SCK/Direct LCD DB7. Used as SCK when communicating with the AT25010A via SPI and when in AT89S8252 ISP mode. Also used as DB7 when the LCD is connected as a direct-connection.
Port 3
P3.0	10	RXD. Connected to the MAX232 for RS-232 serial communication.
P3.1	11	TXD. Connected to the MAX232 for RS-232 serial communication.
P3.2	12	AT25010A Write Protect. Connected to the -WP pin of the AT25010A serial EEPROM, active low. When low the AT25010A will be write protected. When high the AT25010A will not be write protected.
P3.3	13	Direct LCD E/Interrupt 1 Button. Used to drive the LCD E line when the LCD is connected as a direct-connection. Also connected to momentary push-button. If button is pressed this line will be brought low which may activate an external 1 interrupt.
P3.4	14	Direct LCD RW. Used to drive the LCD RW line when the LCD is connected as a direct-connection. Not used if LCD is connected as memory-mapped device.
P3.5	15	Direct LCD RS. Used to drive the LCD RS line when the LCD is connected as a direct-connection.
P3.6	16	WR. Asserted automatically by the microcontroller to write to external memory/memory-mapped devices with the MOVX instruction.
P3.7	17	RD. Asserted automatically by the microcontroller to read from external memory/memory-mapped devices with the MOVX instruction.
Port 2 and Port 0
Both ports 2 and 0 are connected to the address bus and are driven automatically by the microcontroller. None of the pins are used by the SBC for any other functions.

Jumper Settings

Jumper	Function/Description
JP1	P1.0 LED Enable. If JP1 is connected then P1.0 will control LED D6.
JP2	External Access. If JP2 is jumpered to pin 1 (Vcc) then the microcontroller will execute code from the microcontroller's on-chip program memory. If JP2 is jumpered to pin 3 (ground) then the microcontroller will execute code from external EPROM. In this case be sure that a programmed EPROM is installed in the circuit.
JP4	Dallas ISP. If JP4 is jumpered between pins 1 and 2, the DTR pin of the DB9 RS-232 port will drive enable pins of U11 and thereby permit Dallas DS89C420 ISP programming. If JP4 is jumpered between pins 2 and 3 then U11 is permanently disabled and Dallas ISP will not be possible.
JP5	Reset Selection. If JP5 is jumpered to pin 1 then the microcontroller's reset pin will be driven by a traditional reset-capacitor network with capacitor C15. If JP5 is jumpered to pin 3 then the MN13811 reset supervisor will be used to generate the reset signal.
JP6	RTC Battery Backup. JP6 may be used to attach a battery to the DS1307 RTC to drive the clock when the SBC's power is removed. The center pin is Vcc while the left and right pins are ground.

Memory Map

Address Ramge

Function

0000h - 3FFFh

EPROM, if JP2 selects EPROM code execution.

4000h - 4FFFh

LCD Memory-Mapped. Specific addresses access memory-mapped LCD.

4000h	Write Command to LCD
4001h	Write Text to LCD
4002h	Read Command Register from LCD
4003h	Read Text from LCD

5000h - 5FFFh

Keypad Memory-Mapped. Specific address access memory-mapped keypad.

500Eh	Read keypad row 0
500Dh	Read keypad row 1
500Bh	Read keypad row 2
5007h	Read keypad row 3

6000h - 6FFFh

Other 1. Can be used to enable user memory-mapped devices connected via pin 6 of J11.

7000h - 7FFFh

Other 2. Can be used to enable user memory-mapped devices connected via pin 7 of J11.

8000h - FFFFh

Program/RAM. Can serve as XRAM or RAM-based program memory. If a 32k RAM IC is used (62256) then this RAM will occupy all of 8000h - FFFFh. If an 8k RAM IC is used (6264) then this RAM will occupy E000h - FFFFh.

Notes:

EPROM. The EPROM socket is made available primarily for those that wish to use the SBC with a microcontroller that does not include on-chip code memory. In this case the user program or monitor must be loaded into an EPROM and JP2 must be configured to the 2-3 setting.
Non-EPROM Use. If a microcontroller with on-chip code memory is being used (such as an Atmel AT89S8252, Dallas DS89C420, etc.) then the EPROM may be completely omitted.