RTL8308B

2002/01/23

Rev. 2.0

21

6.23 Testing

There are several testing and diagnostic options for the RTL8308B. This section will describe the External SRAM

Test, Production Testing and the External Loopback Test.

6.23.1 External SRAM Test

After RESET signal goes high, the RTL8308B will perform external memory self-test. It performs a worse case

test by changing Address & Data bus bits as much as possible between each access. The whole test takes about

14ms. The corresponding memory error indication bit accessible via serial LED interface will be turn on if any data

read is different from written.

6.23.2 Production Testing

The RTL8308B supports a simple but effective testing function for final production test in the process of switch

manufacturing. If board diagnostic function is enabled, the switch may act as a packet generator to be part of the

production test fixture to test finished switch system on production line. In this mode, the switch generates 16

broadcast packets on each port, from port 0 to port 4/7 sequentially. All other ports except the transmitting port

should received 16 valid packets. If any port failed to receive packets as expected, the switch will turn on the

corresponding RX ERR LED. Otherwise, RXOK LEDs will be lit. During the process of testing, the switch turns

on TXON LED of the transmitting port and RXON LED of all other ports. When the process completed

successfully, the switch will turn on the TESTOK LED. The switch will re-start testing cycle when a trigger signal

applied to the CFGIN pin or when a test cycle timer of 26 seconds expired. Note that all links must operate in full

duplex mode and transmit/receive at 100Mbps. Note that this feature is supported only when the switch in test

fixture and the switch in production are both designed based on the RTL8308B controllers.

6.23.3 Loopback

This feature is designed to simplify field support task for system manufacturers and distributors. In this mode, the

switch should have switch ports connected in pairs using cross-over CAT-5 cables. When external loop-back test is

enabled, the switch sends 16 packets on all active (connected) ports simultaneously. And each active port should

receive exactly 16 valid packets. . If any port failed to receive packets as expected, the switch will turn on the

corresponding RX ERR LED. Otherwise, RXOK LEDs will be lit. During the process of testing, the switch turns

on TXON LEDs and RXON LEDs of all active ports. When the process completed successfully, the switch will

turn on the TESTOK LED. The switch will re-start testing cycle when a trigger signal applied to the CFG_IN pin

or when a test cycle timer of 26 seconds expired. Note that all links must operate in full duplex mode and

transmit/receive at 100 Mbps.