TAB/GAB Readout Control Proposal

updated: 08-Aug-05

Readout of memories in the TAB and GAB is controlled through the VME/SCL card via the PULSE and ACCEPT signals. Behavior of these signals currently depends on the mode in which the VME/SCL card is running: ONLINE or OFFLINE. Given below is a proposal for the sources of these signals and their behavior, depending on the VME/SCL setup.

  1. ONLINE & OFFLINE Modes
  2. Single PULSE/ACCEPT Mode
  3. Periodic PULSE & ACCEPT Modes
  4. Notes

Running Mode Definitions

ONLINE/OFFLINE mode, downloaded to the VME/SCL at initialization, should affect mainly which system clock is used. User generated signals should be allowed in ONLINE mode. However, care must be taken when using Periodic signals in ONLINE as they may conflict with Collect_Status or L1_ACCEPT.

  ONLINE OFFLINE
System Clock Source CLK7 from SCLR Local Oscillator on VME/SCL
PULSE Source(s)
  1. VME: user generated pulse
  2. SCL: CollectStatus bit in the L1 Qualifiers (this is refered to as L1_QUAL7 in the VME/SCL schematics)
  1. VME: user generated pulse
  2. Periodic: pulse on same BC every turn
ACCEPT Source(s)
  1. VME: user generated accept
  2. Periodic: accept generated every N BCs
  3. SCL: L1_ACCEPT bit in the SCL data
  1. VME: user generated accept
  2. Periodic: accept generated every N BCs

SINGLE Mode: User Generated PULSE & ACCEPT

The generation of these signals through VME commands should be changed so that they are independent and so that they occur only once per request.

The following behavior should be implemented for SINGLE mode, which should be selectable by VME command at initialization.

  PULSE (once per cmd) ACCEPT(once per cmd)
Selected by downloading Z = 0 (see below) ???
Generate on next BC=X after receipt of VME command
  • X is a parameter downloaded to VME/SCL at initialization
  • X should also be downloadable during running without requiring re-initialization
 next BC=Y after receipt of VME command
  • Y is a parameter downloaded to VME/SCL at initialization
  • Y should also be downloadable during running without requiring re-initialization
Signal active for A = 1 - 32 BCs
  • A is a parameter downloaded to VME/SCL at initialization
  • A should also be downloadable during running without requiring re-initialization
 1 BC

PERIODIC Mode: Periodically Generated PULSE & ACCEPT

For testing purposes, it is useful to have the ability to generate the PULSE or ACCEPT signals repeatedly with a fixed time interval between them.

The following behavior should be implemented for PERIODIC mode. PERIODIC_PULSE and/or PERIODIC_ACCEPT should be selectable by VME command at initialization.

  PERIODIC_PULSE PERIODIC_ACCEPT
Selected by downloading Z = 1-255 ???
Generate on on BC=X of TURN=Z
  • X,Z are parameters downloaded to VME/SCL at initialization
  • changing X,Z should require re-initialization
  • downloading Z=0 sets PULSE generation to SINGLE mode
 every N BCs
  • N is a parameter downloaded to VME/SCL at initialization
  • changing N should require re-initialization
Signal active for A = 1 - 32 BCs
  • A is a parameter downloaded to VME/SCL at initialization
  • changing A should require re-initialization
 1 BC

Notes

  1. SCLR: The SCL Receiver mezzanine card mounted on the VME/SCL board
  2. Active PULSE: data is written to TAB/GAB memories during the BCs when PULSE is active
  3. PERIODIC_PULSE mode: the PULSEs occur on the same BC,TURN to aid in establishing data synchronization in OFFLINE mode. This mode of operation uses a 6-bit TURN counter (due to limited space in the FPGA) so it will not work in ONLINE mode.
  4. PERIODIC_ACCEPT mode: the frequency at which ACCEPTs are generated needs to be adjustable to aid in L2 testing.