54
Data Device Corporation
www.ddc-web.com
BU-6474X/6484X/6486X
J-07/05-0
IOEN(O)
64
I/O Enable.
Tri-state control for external address and data buffers. Generally not used in buffered mode. When low, indi-
cates that the Mark3 is currently performing a host access to an internal register, or internal (for transparent
mode) external RAM. In transparent mode, IOEN (low) should be used to enable external address and data
bus tri-state buffers.
READYD (O)
62
Handshake output to host processor.
For a nonzero wait state read access, READYD is asserted at the end of a host transfer cycle to indicate that
data is available to be read on D15 through D0 when asserted (low). For a nonzero wait state write cycle,
READYD is asserted at the end of the cycle to indicate that data has been transferred to a register or RAM
location. For both nonzero wait reads and writes, the host must assert STRBD low until READYD is asserted
low.
In the (buffered) zero wait state mode, this output is normally logic "1", indicating that the Mark3 is in a state
ready to accept a subsequent host transfer cycle. In zero wait mode, READYD will transition from high to low
during (or just after) a host transfer cycle, when the Mark3 initiates its internal transfer to or from registers or
internal RAM. When the Mark3 completes its internal transfer, READYD returns to logic "1", indicating it is
ready for the host to initiate a subsequent transfer cycle.
TABLE 53. PROCESSOR INTERFACE CONTROL (CONT.)
SIGNAL NAME
DESCRIPTION
BU-6474XF/GX
BU-6484XF/GX
BU-64863F/GX
PIN
RTAD4 (MSB) (I)
40
RT Address input.
If bit 5 of Configuration Register #6, RT ADDRESS SOURCE, is programmed to logic "0" (default), then the
Mark3's RT address is provided by means of these 5 input signals. In addition, if RT ADDRESS SOURCE is
logic "0", the source of RT address parity is RTADP.
There are many methods for using these input signals for designating the Mark3's RT address. For details,
refer to the description of RT_AD_LAT.
If RT ADDRESS SOURCE is programmed to logic "1", then the Mark3's source for its RT address and parity is
under software control, via data lines D5-D0. In this case, the RTAD4-RTAD0 and RTADP signals are not used.
RTAD3 (I)
39
RTAD2 (I)
24
RTAD1 (I)
45
RTAD0 (LSB) (I)
38
RT_AD_LAT (I)
36
RT Address Latch.
Input signal used to control the Mark3's internal RT address latch. If RT_AD_LAT is connected to logic "0", then
the Mark3 RT is configured to accept a hardwired (transparent) RT address from RTAD4-RTAD0 and RTADP.
If RT_AD_LAT is initially logic "0", and then transitions to logic "1", the values presented on RTAD4-RTAD0
and RTADP will be latched internally on the rising edge of RT_AD_LAT.
If RT_AD_LAT is connected to logic "1", then the Mark3's RT address is latchable under host processor con-
trol. In this case, there are two possibilities: (1) If bit 5 of Configuration Register #6, RT ADDRESS SOURCE,
is programmed to logic "0" (default), then the source of the RT Address is the RTAD4-RTAD0 and RTADP
input signals. (2) If RT ADDRESS SOURCE is programmed to logic "1", then the source of the RT Address is
the lower 6 bits of the processor data bus, D5-D1 (for RTAD4-0) and D0 (for RTADP).
In either of these two cases (with RT_AD_LAT = "1"), the processor will cause the RT address to be latched
by: (1) Writing bit 15 of Configuration Register #3, ENHANCED MODE ENABLE, to logic "1". (2) Writing bit 3
of Configuration Register #4, LATCH RT ADDRESS WITH CONFIGURATION REGISTER #5, to logic "1". (3)
Writing to Configuration Register #5. In the case of RT ADDRESS SOURCE = "1", then the values of RT
address and RT address parity must be written to the lower 6 bits of Configuration Register #5, via D5-D0. In
the case where RT ADDRESS SOURCE = "0", the bit values presented on D5-D0 become "don't care".
RTADP (I)
44
Remote Terminal Address Parity.
This input signal must provide an odd parity sum with RTAD4-RTAD0 in order for the RT to respond to non-broad-
cast commands. That is, there must be an odd number of logic "1"s from among RTAD-4-RTAD0 and RTADP.
TABLE 54. RT ADDRESS
SIGNAL NAME
DESCRIPTION
BU-6474XF/GX
BU-6484XF/GX
BU-64863F/GX
PIN
FLAT PACK AND GULL WING PACKAGES - SIGNAL DESCRIPTIONS BY FUNCTIONAL GROUPS (CONT.)