PCU: fix f_establish_tbf(): always expect Uplink TBF

In response to a CHANNEL REQUEST received on BCCH, the network
would never allocate a Downlink TBF, so we should always expect
an Uplink TBF assignment.

Change-Id: I6b4c108bed39ba9ac9b6144827bc1e20b04333b4
Signed-off-by: Vadim Yanitskiy <axilirator@gmail.com>
diff --git a/pcu/PCU_Tests.ttcn b/pcu/PCU_Tests.ttcn
index 4acde04..48cdd54 100644
--- a/pcu/PCU_Tests.ttcn
+++ b/pcu/PCU_Tests.ttcn
@@ -328,6 +328,7 @@
 /* One phase packet access (see 3GPP TS 44.018, table 9.1.8.1) */
 private const BIT8 chan_req_def := '01111000'B;
 
+/* Establish an Uplink TBF by sending RACH.ind towards the PCU */
 private function f_establish_tbf(out GsmRrMessage rr_imm_ass, uint8_t bts_nr := 0,
 				 uint16_t ra := bit2int(chan_req_def),
 				 uint8_t is_11bit := 0,
@@ -354,7 +355,7 @@
 
 	/* Expect Immediate (TBF) Assignment on TS0/AGCH */
 	return f_pcuif_rx_imm_ass(rr_imm_ass, PCU_IF_SAPI_AGCH,
-				  tr_IMM_TBF_ASS(?, ra, fn),
+				  tr_IMM_TBF_ASS(false, ra, fn),
 				  bts_nr := bts_nr);
 }