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The ZX-24a is a powerful microcontroller for your home automation, industrial control, robotics
or other embedded systems application.
It is an expanded-capacity version of the popular ZX-24 microcontroller, the
primary difference being an additional 2K of User RAM. The ZX-24a also supports pin-change
interrupts on all of the I/O lines.
The heart of the ZX-24a is the Atmel AVR ATmega644 microcontroller running at 14.7MHz.
It is accompanied by some support circuitry on a 24-pin DIP module that is
pin-compatible with the Parallax Basic Stamp and NetMedia BX-24 microcontrollers.
However, many advances have been made with respect to those pioneering products
in order to provide a more powerful and flexible programming platform.
The ATmega644 microcontroller internally has 4096 bytes of RAM of which 3584 bytes (3.5K) are
reserved for direct use by your programs (including dynamically allocated string data).
The remaining 512 bytes are used by the ZX-24a's control program.
The mega644 also has 2048 bytes of internal
EEPROM of which 2016 bytes are usable by your program for non-volatile storage.
The 64K byte internal Flash memory of the Mega644 is used solely by the control program
of the ZX-24a, also known as the Virtual Machine (VM).
User programs are stored in a 32K byte EEPROM on the ZX-24a.
This memory can also be used for storing data (both read-only and read/write) in addition to your program's code.
The Mega644 has other resources available to your program including a high-speed serial port,
analog-to-digital converters, timers and other sub-systems that may be accessed using
routines in the ZBasic System Library. Alternately, some of these resources may be accessed
directly using built-in registers.
You may download a schematic of the ZX-24a (identical to that of the ZX-24) as a
PDF
or as an ExpressPCB .sch file.
To view the latter, you'll have to download free software from
ExpressPCB.
Technical Features
| |
ZX-24a¹ |
BX-24P² |
BS-2IC² |
| Manufacturer |
Elba Corp. |
Netmedia, Inc. |
Parallax, Inc. |
| Package |
24-pin DIP |
24-pin DIP |
24-pin DIP |
| Operating Temperature |
-40 to +85°C |
-40 to +85°C |
0 to +70°C (industrial version available) |
| Processor |
Atmel AVR ATmega644 |
Atmel AVR ATmega8535 |
Microchip PIC 16C57C |
| Power Requirements |
4.5-5.5VDC regulated or 7-20VDC |
3-5.5VDC regulated or 5-24VDC |
5VDC regulated or 5-15VDC |
| Processor Speed |
Up to 14.7MIPS (14.7MHz) |
Up to 7.35 MIPS (7.35MHz ) |
Up to 5MIPS (20MHz) |
| Program Execution Speed |
Up to 175,000 instructions/sec³ |
Up to 83,000 instructions/sec³ |
~4,000 instructions/sec |
| User RAM |
3584 bytes |
401 bytes |
32 bytes |
| Non-volatile Data Memory |
2016 bytes |
480 bytes |
None |
| Program Memory |
32K bytes (8000+ instructions) |
32K bytes (8000+ instructions) |
2K bytes (~500 instructions) |
| Digital I/O pins |
16+3 (note 4) |
16+3 (note 4) |
16 |
| Analog-to-Digital Channels |
Up to 8 channels, 10-bit |
Up to 8 channels, 10-bit |
None |
| PWM Channels |
Two 16 bit |
Requires application code |
One 8-bit pseudo-PWM |
| I2C Support |
1 HW channel, 4 SW channels |
Requires application code |
2 SW channels |
| 1-Wire Support |
Bit and byte level |
Bit level only |
Bit and byte level |
| SPI Support |
4 HW channels |
4 HW channels |
No |
| Synchronous Serial I/O Support |
1-16 bits, MSB or LSB first |
1-8 bits, MSB first only |
1-16 bits, MSB or LSB first |
| Asynchronous Serial I/O Ports |
1-HW, up to 4 SW full duplex |
1-HW, 1 SW full duplex |
1-HW, half duplex SW on any I/O pin |
| X-10 Command Support |
Yes |
Yes |
Yes |
| Multi-tasking Support |
Yes |
Yes |
No |
| External Interrupts |
3 |
1 |
None |
| Pin Change Interrupts |
All I/O lines |
No |
No |
| Analog Comparator Interrupt |
Yes |
No |
No |
| Interval Timer |
Yes |
No |
No |
| Exception Handling Support |
Yes |
No |
No |
| On-board LEDs |
Red, Green |
Red, Green |
None |
| Floating Point Math |
Yes - IEEE 32-bit |
Yes - IEEE 32-bit |
No |
| Advanced Floating Point
Functions (sin, cos, log, etc.) |
System Level |
User Level |
No |
| Programming Interface |
Serial - 115.2K baud |
Serial - 115.2K baud |
Serial - 9600 baud |
| Field Upgradeable System Software |
Yes |
No |
No |
Notes:
1) Items in boldface indicate differences from the ZX-24.
2) Information from manufacturer's documentation and website.
3) Maximum speed based on the instruction b = b + 1 with stack checking disabled.
4) The additional 3 I/O lines are outside of the standard 24-pin DIP format.
5) SW means implemented in system software, HW means hardware implementation.
6) 'User Level' implementation adds code to the compiled program and is slower than 'System Level' implementation.
Specifications subject to correction and change without notice.
A standard serial port is required to download code to the ZX-24a.
If your computer does not have a standard 9-pin serial port but does have a USB port, you may use a USB to serial adapter.
Note, however, that some USB to serial adapters are too slow to be useful with the ZX microcontrollers.
We have found that adapters based on the second generation FTDI chips seem to work well.
The ZBasic IDE, compiler and documentation may be obtained free of charge via the Download page. See the menu at the left.
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