The Models 1691 A and 2891 A Interfaces provide connections for the Model 1821 FASTBUS Segment Manager andInterface through either theIBM AT(1691A) or through CAMAC(2891A). Theconnection is made to the front- panel interface control port using a terminated 34-pin flat ribbon cable. (Maximum length is 3 meters.)
For the IBM AT or compatible, the LeCroy Interactive FASTBUS Toolkit (LIFT) provides a framework from which the user can design, develop, and test FASTBUS acquisition procedures. A subset of FASTBUS standard routines can be employed. Alternately, the user may develop his own custom microcode for more flexibility and perform- ance. This solution has been made even more attractive with the introduction of SONIC, an assembler which provides simple and straightforward source code.
Although not as comprehensive, FORTRAN subroutines for editing and testing FASTBUS acquisition procedures are also provided for the Model 2891A CAMAC to FASTBUS Interface. A subset of the FASTBUS standard rou- tines is also available. Model 1691A IBM PC/XT/AT to FASTBUS Interface
signal Levels: All connector signals are TTL level.
Data Format: 16-bit word on cable, built from two 8-bit host
transfers. Bidirectional data is accompanied by
four Module Address and four Register Address
lines driven from the 1691A to the connected
device.
Data Rate: Each transfer is initiated by a positive going TTL
strobe initiated by the host. Therefore the rate is
dependent upon host computer speed and cable
length. Typical speed using 8 MHz IBM PC-AT
driving 2 meter cable: 2 MB/sec.
Signals: Active low TTL RD, WR, ENB, and BYP for use
with the 1821 are driven by the 1691A.
Compatibility: IBM PC/XT/AT and compatibles. When LIFT is
used, an IBM AT is the recommended host
because of its larger memory capability and hard
disk.
Model 2891A
CAMAC to FASTBUS Interface
Signal Levels: All connector signals are TTL level.
Data Format: 16-bit word on cable. Bidirectional data is accom-
panied by four Module Address lines.
Data Rate: Dependent upon host computer speed and cable
length, The CAMAC Dataway a sychronous
highway that can support rates of up to 1 MHz.
The exact data rate is also dependent on the
action requested of the 1821. ie. Block read of a
slave.
Other Signals: Active low TTL RD, WR, ENB, and BYP for use
with the 1821 are driven by the 2891A. The ACK
line is an active low TTL input from the 1821.
Compatibility: The 2891A has been designed to conform to the
IEEE Std. 583. It should operate properly in
standard CAMAC system.
2891 A CAMAC Commands
Because communication with FASTBUS is non-synchronous, two modes of operation have been implemented in the 2891A; one for use with short cables (under 3 meters), and one for use with long cables. When used in the short cable mode (2891 compatible) of operation, the CAMAC command F(O)-A(0-7) will read the contents of the 1821 registers 0 through 7. The CAMAC command F(16)-A(0-7) will write data into the 1821 registers 0 through 7. All CAMAC commands must be accompanied by the CAMAC station number - N where N represents the slot in the CAMAC crate.
When used in the long cable mode (default), two CAMAC com- mands must be issued for each CAMAC operation. In order to read the ith register, the command F(O)-A(i) must be issued, followed by the command F(l)-A(O) where i can be any integer from 0 to 7. To write data to the ith register, the command F(16)-A(i) must be issued, followed by the command F(17)-A(O).
Since the Model 2891A has the capability to address multiple 1821's, the Module Select Register must be loaded with the address of the selected 1821. The Module Select Register is loaded by the command F(l7)-A(l) and read by the command F(1)-A(1). This register is a 6-bit register with the lower 4 write lines (W1-W4) defining the module address. W5 is a Port Enable bit. It W5=0, then the front-panel port is enabled. If W5=1, then the Auxiliary port is enabled. W6 is the Bypass bit. If W6=0, then the 2891 A is in Bypass mode and the data on W 1 through W4 is ignored. If W6=1, then W1 through W4 is assumed to contain the address of the 1821 to be addressed. (Note: Executing a read cycle when using Bypass addressing will result in all 1821's connected to the 2891 A bus presenting their register contents on the bus simultaneously creating unintelligible results.)
An X=l response is generated on all valid N-F-A commands where N represents the CAMAC station number (1-23), F represents the CAMAC function code (F=O, 1, 16, 17), and A represents the CAMAC sub-address (0-15). A Q=1 response is generated for F(l) commands if the 1821 responded to the last F(O) or F(16) com- mand. All other F codes return Q=0.
CAMAC C, Z, and I are not implemented in this module.