Service manual

FO-4700U
FO-47UC
5 – 13
HD813201F (IC12) Terminal descriptions
Code Terminal No. I/O Function
MAS 74 O Memory Address Strobe (Memory address strobe terminal). When MAS
becomes "high" level, it indicates that address is output to MA/MD0 thru
MA/MD15 and MA16 thru MA21.
UDS 27 Three-state output Upper Data Strobe (high-order data strobe terminal). When UDS becomes "low"
level, it indicates that IDP201 uses the high-order byte of the image bus.
LDS 23 Three-state output Upper Data Strobe (low-order data strobe terminal). When LDS becomes "low"
level, it indicates that IDP201 uses the low-order byte of the image bus.
MDEN 25 O Memory Data Bus Enable (Memory data bus enable terminal). When MDEN
output terminal becomes "low" level, it indicates that valid data are present in
MA/MD0 thru MA/MD15. This output terminal is used to control the output of the
bidirectional bus buffer on MA/MD0 thru MA/MD15.
MA/MD 0 79 I/O,
MA/MD 1 77
Three-state output
MA/MD 2 3
MA/MD 3 78
MA/MD 4 5
MA/MD 5 2
MA/MD 6 6
MA/MD 7 4
MA/MD 8 8
MA/MD 9 7
MA/MD10 12
MA/MD11 9
MA/MD12 14
MA/MD13 13
MA/MD14 15
MA/MD15 16
MA16 71 Three-state output
MA17 11
MA18 30
MA19 31
MA20 50
MA21 51
MR 26 Three-state output Memory Read (Memory read terminal). When MR is turned to "low" level,
IDP201 reads the data from the image memory.
MW 28 Three-state output Memory Write (memory write terminal). When MW is turned to "low" level,
IDP201 writes the data in the image memory.
IOR 35 Three-state output I/O Read (I/O read terminal). When IOR is turned to "low" level, IDP201 reads
the data from I/O device on the image bus. However, it is limited at DMA transfer
during data transfer with the transfer command and the coding process.
IOW 36 Three-state output I/O Write (I/O write terminal). When IOW is turned to "low" level, IDP201 writes
the data in I/O device on the image bus. However, it is limited at DMA transfer
during data transfer with the transfer command and the decoding process.
DRQTI 39 I DMA Request Input (DMA request input terminal). When I/O device on the
image bus requests DMA for IDP201, DRQTI becomes "high" level.
DACKO 38 O DMA Acknowledge Output (DMA acknowledge output terminal). When this
output terminal is turned to "low" level, IDP201 informs to the peripheral
devices on the image bus that DMA operation is approved.
DMA 32 O Direct Memory Access (Direct memory access terminal). When DMA output is
turned to "low", it indicates that DMA transfer is executed.
In the coding process, the data is transferred from the I/O device (scanner) to
the image memory.
In the decoding process, the data is transferred from the image memory to
I/O device (printer).
Memory Address Data Bus 0 thru 15 (Memory address data bus). In this bus for
image bus operation, the address and data are multiplexed. MA/MD0 thru
MA/MD15 are used as follows.
(1) When MAEN is "low" and MAS is "high", it is used as the output address line.
(2) When both MAEN and MDEN are "low" in the reading cycle, it is used as the
input data line.
(3) When both MAEN and MDEN are "low" in the writing cycle, it is used as the
input data line.
Memory Address Bus 16 thru 21 (memory address bus). When MAEN is "low"
and MAS is "high", it is used as the output address line.