Interface

T.S. Ikin

• Introduction

• Adlink SCSI Signals Relevent to COBRA

• Data Lines used as Control Signals

• Data from the Samplers When DIRECTION = 1 (SAMPLING Mode)

• Data from the Adlink Board When DIRECTION = 0 (INITIALISATION Mode)

• Initialisation Registers

• Header Word Generation

• Test Modes

• Sampling Mode Sequence of Operation

• LED's on the front of Interface Board

The Interface Board sits logically between the Samplers and the Adlink Board.

Features

• Drive the 32 bits of the sampled data down a SCSI cable 10m (max) to the Adlink Board
• Registers provided for initial settings such as sampling rate
• Acts as a path to set registers on external devices such as the samplers and the Local Oscillators
• Allows for precise synchronisation to the Station Clock pulses so that timing accuracy is assured
• Produces header information to allow for data error detection
• Four test modes available for transmission rate evaluation

Two Auxilary signals output from the Adlink board have been used to control the interface board

Where:

• RI is Right Hand In-phase
• RQ is Right Hand Quadrature
• LI is Left Hand In-phase
• LQ is Left Hand Quadrature

Data flow is controlled by the interface in a non-handshaking mode. Refer to the Adlink manual, section 4.10.2 "Digital Input DMA in External Clock Mode" Data is clocked into the Adlink board on the rising edge of the DI-REQ signal.

Where:

• A is an 8-bit address code pointing to a register
• D is an 8-bit data word to go into the specified register

Data flow is controlled by the Adlink Board in a handshaking mode. This is because there are some time sensisitve registers to be filled. The Interface Board, "handshakes" when data is latched. Refer to the Adlink manual, section 4.11.2 "Digital Output DMA in Handshaking Mode." Data is clocked onto the Interface Board on the rising edge of the DO-REQ signal, as generated by the Adlink Board. The Interface Board acknowledges receipt of data by asserting the DO-ACK line.

• Adjacent two Sampler Board attenuator settings and frequency channel
• Frequency setting of LO's associated with Sampler Boards

1. Manual: DIP switches on the front of the Interface Board may be used to program the initial settings of all registers. There are two sets of eight DIP switches, one set acts as ADDRESS, and the other as DATA. A push button "Enters" the DATA onto the selected ADDRESS.
2. Remote: Similar to Manual Mode, but DATA and ADDRESS information is sent over the data cable from the DMA interface board.

Once each second two header words are produced in the data. This appears in the place of sampled data following the rising edge of the station 1PPS signal. The following tables describe the words transmitted. Briefly, there are flag words, a count word and identifier words. Note that this is not produced in the test modes.

Where:

• c is one bit of the Counter Word
• ID is one bit of the Interface Board Identifier Word

When the three SPEED bits in the Interface Register are set to 100 ; 101 ; 110 ;or 111 the Interface Board enters a test mode state. The board produces 32 bits of count word incrementing at 5,10,20 and 40 Million Bytes per second. This runs continuously while the two control bits (AUXO0, and AUXO1) are asserted.

When all registers are correctly set, either by DIP switches or Remote Control, sampling may begin. This is done by setting DIRECTION=HIGH, and ARM=HIGH. Sampling will commence synchronously with the following round ten second. The first two words to be transmitted will be the two 32 bit header words as described. Following this will be the data. One 32 bit word is transmitted per sample period per sampler board selected. SAMPLER0 data is transmitted first then SAMPLER1 data. This will continue until the next 1PPS, when the header words will again be transmitted. This state will continue until ARM is cleared to low.

	SPEED0
	SPEED1
	SPEED2
	SAMPLER0
	SAMPLER1
	ARM
	DIRECTION
	(ARM AND DIRECTION)
	SPARE
	LO_LOCK0
	LO_LOCK1