S-1990
Encyclopedia
The S-1990 is a VLSI integrated circuit
created by NEC
for the MSX
Turbo R home computer
, and is called the "Turbo R bus controller".
Together with a R800 CPU and a T9769 MSX-Engine
chip it forms the heart of a Turbo R MSX-system.
with the older MSX 1, MSX 2 and MSX 2+ systems the Turbo R also uses the Z80 CPU inside the T9769. The S-1990 is used to control the bus access so that either the R800 or the Z80 inside the T9769 can access the memory and peripherals. Because of the comparatively greater speed of the R800 (28.636360 MHz compared to the 3.58 or 7.16 MHz of the Z80) the S1990 also implements a "wait state" mechanism to slow down access to slower legacy devices (especially for the peripherals in the T9769, in particular the video display controller) that otherwise could not keep up with the R800. It also implements hardware assisted software debugging
.
Controller
Debug function
Chip package: 160 pins QFP
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
created by NEC
NEC
, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
for the MSX
MSX
MSX was the name of a standardized home computer architecture in the 1980s conceived by Kazuhiko Nishi, then Vice-president at Microsoft Japan and Director at ASCII Corporation...
Turbo R home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
, and is called the "Turbo R bus controller".
Together with a R800 CPU and a T9769 MSX-Engine
MSX-Engine
An MSX-ENGINE chip is a specially developed integrated circuit for home computers that are built according to the MSX specifications.Generally, such a chip combines the functions of many separate, older/simpler chips into one...
chip it forms the heart of a Turbo R MSX-system.
Development and design
The S-1990 was especially developed for "MSX turbo R computers" which are outfitted with an ASCII R800-processor. To retain backward compatibilityBackward compatibility
In the context of telecommunications and computing, a device or technology is said to be backward or downward compatible if it can work with input generated by an older device...
with the older MSX 1, MSX 2 and MSX 2+ systems the Turbo R also uses the Z80 CPU inside the T9769. The S-1990 is used to control the bus access so that either the R800 or the Z80 inside the T9769 can access the memory and peripherals. Because of the comparatively greater speed of the R800 (28.636360 MHz compared to the 3.58 or 7.16 MHz of the Z80) the S1990 also implements a "wait state" mechanism to slow down access to slower legacy devices (especially for the peripherals in the T9769, in particular the video display controller) that otherwise could not keep up with the R800. It also implements hardware assisted software debugging
Debugging
Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware, thus making it behave as expected. Debugging tends to be harder when various subsystems are tightly coupled, as changes in one may cause bugs to emerge...
.
Technical specifications
- For the ASCII R800 processor
- For the Z80 processor inside the T9769 MSX-Engine
- For ZilogZilogZilog, Inc., previously known as ZiLOG , is a manufacturer of 8-bit and 24-bit microcontrollers, and is most famous for its Intel 8080-compatible Z80 series.-History:...
Z80-timing emulation - For MSX-cartridge slot management, -memory control and I/O address decoderAddress decoderIn digital electronics, an address decoder is a decoder circuit that has two or more bits of an address bus as inputs and that has one or more device selection lines as outputs. When the address for a particular device appears on the address bus, the address decoder asserts the selection line for...
- For memory access, I/O control, RFSH#/M1#-simulation
- For access to programmable peripherals (The S-1990 does not include these peripherals, they are contained within the T9769, but it controls access to them, and in particular it slows down the R800 CPU when accessing these peripherals, especially when accessing the VDP).
- Programmable Peripheral Interface compatible with the Intel i8255Intel 8255The Intel 8255 Programmable Peripheral Interface chip is a peripheral chip originally developed for the Intel 8085 microprocessor, and as such is a member of a large array of such chips, known as the MCS-85 Family. This chip was later also used with the Intel 8086 and its descendants.It was later...
-PPI - MegaRom-mapper
- DRAMDynamic random access memoryDynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1...
-mapper - KanjiKanjiKanji are the adopted logographic Chinese characters hanzi that are used in the modern Japanese writing system along with hiragana , katakana , Indo Arabic numerals, and the occasional use of the Latin alphabet...
ROM-interface - system timer
- Sound chipSound chipA sound chip is an integrated circuit designed to produce sound . It might be doing this through digital, analog or mixed-mode electronics...
- Programmable Sound GeneratorSound chipA sound chip is an integrated circuit designed to produce sound . It might be doing this through digital, analog or mixed-mode electronics...
, compatible with the General InstrumentGeneral InstrumentGeneral Instrument was an electronics manufacturer based in Horsham, PA specializing in semiconductors and cable television equipment. The company was active until 1997, when it split into which was later acquired by Vishay Intertechnology in 2001, CommScope and NextLevel Systems General...
AY-3-8910 - pulse code modulation (PCM)
- PCM-samplingSampling (signal processing)In signal processing, sampling is the reduction of a continuous signal to a discrete signal. A common example is the conversion of a sound wave to a sequence of samples ....
- Programmable Sound Generator
- Video Display ControllerVideo Display ControllerA Video Display Controller or VDC is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system...
: YamahaYamahaYamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...
V9958Yamaha V9958The Yamaha V9958 is a Video Display Controller used in MSX 80s home computers. More specifically, the "TIM" upgrade to the TI-99/4A, MSX 2+ and MSX turbo R.... - floppy diskFloppy diskA floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
-interface
- Programmable Peripheral Interface compatible with the Intel i8255
- For the execution of kernel functions
- For the pause function
Debug function
- Memory address comparator: When the address bus of the R800 is watched and a designated address is accessed, an NMINon-Maskable interruptA non-maskable interrupt is a computer processor interrupt that cannot be ignored by standard interrupt masking techniques in the system. It is typically used to signal attention for non-recoverable hardware errors...
is generated. The function is enabled when address bus line A8 is pulled low while resetting the S-1990. - NMI-status register: When the above-mentioned address comparator is triggered this register contains the source of the NMI.
- Debug monitor for the cartridge slot register: When the above-mentioned address comparator is triggered, while operating the debug monitor, this control register controls the slot environment.
- NMI-return address register: contains the return address to the user program, so it can return to the original program after exiting the debugger.
- Breakpoints: When debug mode is enabled, pressing the pause key breaks the user program and jumps to a debugging Monitor in ROM.
Chip package: 160 pins QFP
QFP
A QFP or Quad Flat Package is a surface mount integrated circuit package with leads extending from each of the four sides. Socketing such packages is rare and hole mounting is not possible. Versions ranging from 32 to 304 pins with a pitch ranging from 0.4 to 1.0 mm are common...