IBM 6400 Maintenance Information Manual page 48

Chapter 4
CMX Controller Board
NVRAM
A 8K x 8 bit Non-Volatile battery-backed static RAM (NVRAM) device
provides for the storage of configuration and system statistical data.
VX ASIC
The VX is a multifunction custom gate array ASIC containing all the logic for
the DC that is not contained in the 68EC030 processor. The VX provides the
following services:
•
Memory Access Controller
•
DRAM Controller
•
Flash Controller
•
Two DMA Channels
•
Operator Panel Interface
•
"Dot Plucking" and Adjacent Dot Checking
•
"Cajun" Bus Interface
•
Host I/O and Diagnostic Port
Memory Access Controller All 030 addresses go through the VX ASIC. The
VX handles all address decoding, chip selects, DTACKs, and so on.
DRAM Controller
The VX supports up to four banks of page mode DRAM.
FLASH Controller
The VX supports up to four banks of flash memory.
DMA Channels
The VX provides two channels for direct memory access. These channels
move data from the host interface or expansion bus to the DRAM and vice
versa. One address is an I/O address, the other is a memory address with
auto-increment.
Operator Panel Interface
The VX operator panel interface consists of five lines: serial clock, serial data,
and three select lines. It is the VX that handles all parallel-to-serial (and vice
versa) conversion to and from the panel, as well as any special timing needed
when toggling select lines, etc.
"Dot Plucking" And Adjacent Dot Checking
"Dot Plucking" is a specialized DMA function that removes dot data from a dot
image buffer in DRAM in a programmable manner, serializes it, and sends it
to the hammer bank. This function is actually controlled by the EC (see page
49), which has access to the VX through the "Cajun" Bus Interface.
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